Anal. Methods Environ. Chem. J. 5 (3) (2022) 5-18

Research Article, Issue 3

Analytical Methods in Environmental Chemistry Journal

Journal home page: www.amecj.com/ir

AMECJ

Ultraviolet-activated sodium perborate process (UV/SPB) for

removing humic acid from water

Ahmed Jaber Ibrahim a,*

a Scientic Research Center, Al-Ayen University, ThiQar 64011, Iraq

ABSTRACT

Humic acid (HA) has a complex chemical composition and the ability

to chelate, adsorb, and exchange ions with organic and inorganic

contaminants in bodies of water, which worsens water quality and

poses a threat to human health and the environment. In this research,

an Ultraviolet-activated sodium perborate (UV/SPB) symbiotic

method (UV/SPB) was developed to eliminate humic acid in water.

The major synergistic and degradative processes of the humic acid

were investigated, as well as the impact of the starting humic acid

concentration, sodium perborate dose, and primary pH value on

the humic acid elimination. Results indicate that just 0.5 % and

1.5 % of humic acid were eliminated mostly by sole UV and sole

sodium perborate (SPB) methods, respectively. More effectively than

other methods, UV/SPB removed humic acid with an efciency of

88.83%. An experiment using free radicals to mask them revealed

that the primary catalyst for humic acid removal is the hydroxyl

radical generated by sodium perborate activation. The excitation-

emission matrix spectroscopy, Ultraviolet-visible absorption (UV-

Vis) spectrum, absorbance ratio values, specic Ultraviolet-visible

absorbance values (SUVA), and UV/SPB method performance

ndings demonstrated the UV/SPB method’s capability to degrade

and mineralize humic acid.

Keywords:

Absorption,

UV-vis spectrum,

Environment,

Contaminants,

Humic acid

ARTICLE INFO:

Received 3 June 2022

Revised form 9 Aug 2022

Accepted 28 Aug 2022

Available online 29 Sep 2022

*Corresponding Author: Ahmed Jaber Ibrahim

Email: ahmed.jibrahim@alayen.edu.iq

https://doi.org/10.24200/amecj.v5.i03.191

1. Introduction

Humic acid, a non-regular macromolecular

polymer formed over a long period by the

polymerization of various biological remnants, is

the principal component of natural organic matter

(NOM) [1]. The complex chemical composition of

humic acid and the presence of numerous organic

functional groups, including hydroxyl(-OH),

carboxyl(-COOH), carbonyl(C=O), methoxy(-

O-CH3), and quinone groups (–(C(=O)–), make

it able to chemically adsorb, exchange ions, and

physical chelation with contaminants in bodies

of water that are both organic and inorganic. This

compromises the water quality and endangers the

ecosystem and public health [2]. Environmental

studies now have one goal guring out how to

eliminate humic acid from water properly and

effectively. Physical and chemical oxidation

techniques are the primary means of regulating

humic acid in water. The coagulation method [3],

occulation method [4], and adsorption method [5]

are physical techniques for removing humic acid.

However, these techniques transport humic acid

into the solid phase; further solid waste processing

is still necessary. Due to the rapid degradation and

mineralization of humic acid, chemical oxidation

is of major interest [6]. Commonly used chemical

------------------------

6Anal. Methods Environ. Chem. J. 5 (3) (2022) 5-18

oxidation processes for treating organic wastewater

include the photocatalysis method [7-9], The Fenton

oxidation method [10], and the electrochemical

oxidation method [11]. Despite this, each of these

processes has drawbacks, including difcult

reaction conditions and complicated operations.

The in situ oxidizing agent sodium perborate

(SPB, NaBO3) is frequently employed. In contrast

to sodium percarbonate, cyclic perborate ions

(B2O8H4

-2), which are made up of two peroxide

chains lacking BO3

- anions, are present in

sodium perborate instead of being associated

with inorganic salt and hydrogen peroxide [12].

After being dissolved in water, sodium perborate

creates hydrogen peroxide steadily, making it an

effective hydrogen peroxide alternative [13]. Solid

sodium perborate is safer, simpler to carry, and

easier to store than liquid hydrogen peroxide. The

formation of hydroxyl radicals (.OH) can occur

during sodium perborate activation across a broad

range, which is crucial. The primary methods for

sodium perborate activating are ultraviolet light

[14] and transitional metal ions [15]. Scientists

have utilized UV-activated perborate to remove

organic pollutants [13]. Furthermore, the perborate

is often used as an oxidant in homogeneous photo-

Fenton and heterogeneous Fenton-like reactions to

remove colorant and phenolic compounds [12,16].

Of these, the UV-activated process is simple to

use, secure, and free of other pollutants, allowing

it to effectively stimulate hydrogen peroxide to

break down organics in sewage [17,18]. Though

UV-activated peroxide as well as the UV-activated

sodium perborate (UV/SPB) approach has been

used to eliminate organics from water, reports

of the elimination of HA using UV-activated

SPB are infrequent. To reduce humic acid in an

aqueous solution, it was important for this research

to construct a UV/SPB symbiotic system (UV/

SPB). The inuences of the primary humic acid

concentration, sodium perborate concentration,

and starting pH value on humic acid cleansing

were investigated using the practical and effective

spectrophotometric approach [19]. Using a free

radical masking test, the primary compounds

produced in the symbiotic system for removing

humic acid were identied. The degradation process

was carefully investigated using UV spectrum,

total organic carbon, and 3-dimensional excitation-

emission matrix spectroscopic (3D-EEM).

2. Material and Methods

2.1. Chemicals

Every chemical was obtained with the highest level

of purity, including humic acid (M.wt 2485 dalton,

CAS1415-93-6, Merck Millipore Co., USA),

Sodium perborate (NaBO3, SPB, CAS10486-00-7,

Weifang Haizhiyuan Chemistry and Industry Co.,

China), Sodium sulfate (Na2SO4, CAS7757-82-

6, Tokyo Chemical Industry Co., Japan), Sodium

hydroxide (NaOH, CAS1310-73-2, Weifang

Haizhiyuan Chemistry and Industry Co., China),

Sulfuric acid (H2SO4, CAS7664-93-9, Merck

Millipore Co., USA), Sodium carbonate (Na2CO3,

CAS497-19-8, Merck Millipore Co., USA), Sodium

dihydrogen phosphate (NaH2PO4, CAS7558-80-

7, Tokyo Chemical Industry Co., Japan), Sodium

nitrate (NaNO3, CAS7631-99-4, Merck Millipore

Co., USA), Sodium bicarbonate (NaHCO3, CAS144-

55-8, Weifang Haizhiyuan Chemistry and Industry

Co., China), Sodium chloride (NaCl, CAS7440-23-

5, Weifang Haizhiyuan Chemistry and Industry Co.,

China), and Tertiary butanol (TBA, CAS75-65-0,

Merck Millipore Co., USA).

2.2. Experiment

The humic acid removal studies were carried

out at 25oC. The UV led (16 W, 254 nm) was

positioned above the beaker at a length of 3.5 cm.

The magnetic stirrer held the beaker, which served

as the chemical reactor. In this study, the UV

irradiation was estimated to be 35.2 Jm cm-2 for an

hour. A certain amount of the humic acid solution

was diluted to 100 mL before the experiment.

The sodium perborate was then added to the HA-

imitated wastewater, and light irradiation started

the reaction. 2.5 mL aliquots were taken out at

predetermined intervals to measure the absorbance.

Every experiment was run at least twice. Tertiary

butanol was utilized as the scavenger to conrm the

UV/SPB process for removing humic acid in water Ahmed Jaber Ibrahim

creation of hydroxyl radicals.

2.3. Analysis and Procedure

To determine the effectiveness of the humic acid

removal process, the solution’s absorbance was

measured using a UV-vis spectrophotometer and

an external reference technique at a wavelength

of 254 nm [20]. The mathematics formula read in

Equation 1 as follows:

HA elimination efciency = (C0 – Ct / C0)×100 %

(Eq.1)

where Ct represents the humic acid quantity at the

time of treatment t, and C0 represents the initial

humic acid quantity.

A variety of distinct UV-vis adsorption patterns

were used to determine the change in the humic

acid molecule structure. absorbance values were

determined by spectrophotometer at wavelengths

(nm) at 203, 250, 253, 254, 365, 436, 465, and

665, respectively [21]. To characterize the changes

in the humic acid molecule structure, continuous

variations in the solution’s absorbance range (200-

800 nm) were also examined (Schema 1). A TOC

tester was used to measure total organic carbon

(TOC). Ax (sample absorbance at x nm) and TOC

were used to determine specic UV absorbance

(SUVAx) which was shown in (Equation 2) [22].

(SUVAx) = (Ax / TOC) × 100%

(Eq.2)

The mechanism of the humic acid degradation

was investigated using the 3D-EEM spectrum.

The corresponding apertures were 10 and 5 nm,

respectively, while the wavelength limits for the

emission and stimulation ranges were (280-550

nm) and (200-400 nm), respectively.

Schema 1. Removal procedure for the humic acid and determined

by the UV-Vis spectrophotometer

3. Results and discussion

3.1. Study of the humic acid elimination by UV/

SPB process

3.1.1.Performance comparison of the humic acid

elimination in various systems

First, three processes—UV, SPB, and UV/SPB—

were examined for their ability to remove the humic

acid, as shown in Figure 1 The following were the

experimental parameters: starting pH 3, 10 mg L-1

of the humic acid, 1 mmol L-1 of Sodium perborate,

and 10 mg L-1 of the humic acid.

The single UV treatment took 1 hour to remove

0.5 % of the humic acid, which was barely

eliminated. The single sodium perborate treatment

had a negligible effect on the removal of the

humic acid, with a decolorization ratio of 1.5%

after an hour. The UV/SPB process had a higher

decontamination efciency of 88.83 % than the

other two processes, which rose by a smaller

amount. In addition, when the humic acid was

removed using UV light and hydrogen peroxide

with the same molecular weight, the elimination

ratio was only 40.2 % after 1 hour (60 min). It

has the same effect as hydrogen peroxide when

Sodium perborate is dissolved in water (Equation

3) [12], which is why it is frequently employed

for in situ chemical oxidation. Hydrogen peroxide

was produced in the only Sodium perborate

system, but because it cannot be activated to

produce hydroxyl radicals, very little humic acid

was eliminated. In the UV/SPB system, hydrogen

peroxide produced from Sodium perborate can

generate hydroxyl radicals after being exposed

to UV (Equation 4) [14], This might oxidize and

damage the functional groups in the structure of

the molecule of the humic acid.

NaBO3+H2O NaBO2 +H2O2

(Eq.3)

H2O2+hv 2.OH

(Eq.4)

Anal. Methods Environ. Chem. J. 5 (3) (2022) 5-18

Fig. 1. Performance comparative of humic acid elimination in various systems

3.1.2.Humic acid concentration effect

Figure 2a illustrates the impact of the humic acid

concentration on the humic acid elimination by the

UV/SPB system. The optimized parameters were

the sodium perborate concentration of 1 mmol L-1

and primary pH of 3. The elimination ratio dropped

as the humic acid primary concentration raised.

After 1 hour, the elimination ratio dropped from

89.81% to 70.81% when the humic acid content

increased from 5 to 15 mg L-1.

Because there weren’t enough oxygen radicals

generated by the system to completely oxidize

all of the pollutants in the solution, it proved that

the oxygen radicals generated during the UV/

SPB system were continually used. Additionally,

as humic acid concentration gradually increased,

the competition between humic acid molecules

and oxygen radicals grew more intense. Further,

the increased humic acid content would absorb

more UV rays [23], preventing hydrogen peroxide

activation and the subsequent generation of

hydroxyl radicals (.OH), which resulted in a

decrease in the elimination of the humic acid.

3.1.3.Effect of sodium perborate concentration

Reactive radicals are produced by the Sodium

perborate (SPB), which is important for the

symbiotic mechanism. Investigations were done

on the effect of Sodium perborate concentration on

humic acid removal (Figure 2b). A concentration

of humic acid of 10 mg L-1 and a pH of 3 was used

in the test. After 1 hour, the Sodium perborate

concentration was increased from 0.25 to 1.0 mmol

L-1, and the humic acid elimination ratio increased

from 53.0 to 88.83 %. The number of active

oxygen radicals in the system was increased with

an increase in Sodium perborate concentration,

which aided in the elimination of humic acid.

Nevertheless, In excess, Sodium perborate would

hunt the hydroxyl radical and produce the peroxy

hydroxyl radical (HO2

.) (Equation 5) [24]. peroxy

hydroxyl radical has a weaker redox potential than

hydroxyl radical. Consequently, the reduction in

humic acid elimination was caused by the excess

Sodium perborate (2 mmol L-1).

.OH +H2O2 H2O + HO2

(Eq.5)

3.1.4.Primary pH effect

Figure 2c illustrates the impact of various initial pH

levels on the elimination of humic acid following UV/

SPB processing. The Sodium perborate concentration

was 1 mmol L-1 and the humic acid concentration

was 10 mg L-1 during the experiment. After 1 hour,

the pH value increased from 3 to 11, while the humic

acid elimination fell from 88.83% to 58.4%. Strongly

acidic conditions render the humic acid molecule

neutral, resulting in more photochemical activity

than under neutral or basic conditions. The pH has an

impact on the redox potential Energy(OH, H2O ) as well.

The redox of Energy(OH, H2O ) decreases from 2.61 V to

2.14 V as pH rises from 3 to 11 [25]. The alkaline state

would cause the hydroxyl radical to undergo a reaction

(Equation 6-8) that would change it into O.- (E = 1.78

V), which had a lower oxidation capability than the

hydroxyl radical. When the pH reaches 11, the main

form of hydrogen peroxide changes to HO2

-, which

reacts with hydroxyl radical (.OH) at a faster rate than

hydrogen peroxide does [27], therefore going to lead

using more hydroxyl radical in the process.

OH- + .OH H2O + O-

(Eq.6)

HO2

-+ .OH OH- + HO2

. (k= 7.5 × 109)

(Eq.7)

.OH + H2O H2O + HO2

. (k= 2.7 × 107)

(Eq.8)

3.1.5.Elimination of humic acid in various water

bodies

Figure 2d shows how the UV/SPB system removes

humic acid from various water bodies. Following

a one-hour reaction, the amounts of humic acid

removed from tap water, lake water, and DI

(deionized water) were 88.83%, 59.63%, and 47.53

%, respectively. It shows that both tap water and lake

water prevented humic acid from being eliminated.

These were the underlying causes. First, the hydroxyl

UV/SPB process for removing humic acid in water Ahmed Jaber Ibrahim

radical produced by the UV/SPB process would face

competition from other naturally occurring organic

substances in the lake. Second, the attendance of

several anions in both tap water and lake water may

limit the action of the oxidizing agents, decreasing

the effectiveness of removing humic acid.

3.1.6.Common anions’ inuence on water

Figure 3a illustrates how common anions including

HCO3

-, CO3

-2, NO3

-, SO4

-2, Cl-, and H2PO4

- affect

the removal of humic acid by the UV/SPB process.

When the Carbonate anion (CO3

-2) concentration

was dropped from 1 to 10 mmol L-1, as shown in

Figure 3a, the elimination efciency dropped from

63.7 to 44.9 %. The cause of the decline in humic

acid elimination was that the hydroxyl radical

produced by the process was used by Carbonate

anion (CO3

-2) to create CO3

.- with a low oxidation

capability (Equation 9) [28].

.OH + CO3

-2 CO3

.- + OH- (k= 4.2× 108) (Eq.9)

According to Figure 3b, the humic acid elimination

efciency rapidly declined from 74.2 to 53.5

% during 1 hour when the HCO3

- concentration

rose from 1 to1 to 10 mmol L-1. The system also

converted hydroxyl radicals into HCO3

- (Equation

10). In addition, the HCO3

- addition would result in

a rise in the pH of the solution [29].

.OH + HCO3

- CO3

.- + H2O (k= 4.2×108)

(Eq.10)

In Figure 3c, the elimination of humic acid reduced

from 84.1 % to 79.9 % as the chlorine anion (Cl-)

was increased from 1 to 30 mmol L-1. more excess

chlorine anion would use more hydroxyl radicals

and create more chlorine radicals (Equation 11,12).

Therefore, the decrease in humic acid elimination

was caused by the loss in oxidation capability [30].

.OH + Cl- ClOH.- (k= 4.3×109)

(Eq.11)

Cl- + Cl- Cl2

.- (k= 8×109)

(Eq.12)

Figure 3d shows that the humic acid elimination

ratio decreased with increasing Nitrate anion

(NO3

-) addition. The humic acid elimination was

reduced to 33.4 % when 20 mmol L-1 of Nitrate

anion was introduced. Reactive nitrogen species

(NO2

.) (E0 = 0.867 V), can be produced when UV

ray activated Nitrate anion which has reduced

oxidation capability and also would be damaged

through the UV/SPB process (Equation 13-15)

[31]. Additionally, Nitrate anion could use hydroxyl

radical immediately (Equation 16) [32].

NO3

- + hv NO2

. + O.-

(Eq.13)

NO3

- + hv NO2

- + O

(Eq.14)

2NO2

. + H2O NO3

- + NO2

- + 2H+

(Eq.15)

NO3

- + .OH NO3

. + OH- (k= 4×105)

(Eq.16)

Figure 3e demonstrates that the humic acid elimination

activity was unaffected by the rise in sulfate anion

(SO4-2) quantity. The sulfate anion concentration was

increased to 20 mmol L-1, which resulted in an 88.0 %

increase in humic acid elimination effectiveness. The

literature claims that sulfate anion does not interact

with the reactive species produced in the system

[33,34]; hence it has no impact on eliminating humic

acid. As shown in Figure 3f, the increase of H2PO4

anion little affected the humic acid elimination. The

humic acid removal efciency decreased from 86.3 %

to 82.4 % as the Dihydrogenphosphate anion (H2PO4

) level increased from 10 to 30 mmol L-1. Although

Dihydrogenphosphate anion and hydroxyl radical

can combine to generate the hydrogen phosphate

radical (HPO4

.) (Equation 17) [35], The elimination

of humic acid wouldn’t be impacted because of the

highly sluggish reaction rate.

H2PO4

-+ .OH HPO4

. + H2O (k= 2×104)

(Eq.17)

Anal. Methods Environ. Chem. J. 5 (3) (2022) 5-18

UV/SPB process for removing humic acid in water Ahmed Jaber Ibrahim

Fig. 2. Effect of several factors during UV/SPB system on Humic acid elimination:

a) Humic acid concentration, b) Sodium perborate concentration,

c) primary pH, d) UV/SPB elimination of Humic acid in various waterbodies

3.2. Mechanism of UV/SPB humic acid

elimination

3.2.1.Examining Scavenging

Tertiary butanol (TBA) had the ability to remove

hydroxyl radical from the process of oxidation

(kTBA,

OH = 3.8-7.6×108) [36]. The effect of Tertiary

butanol adding on the elimination of humic acid

in the UV/SPB process is shown in Figure 4. The

empirical parameters were starting pH 3, humic acid

concentration of 10 mg L-1, and Sodium perborate

dosage of 1.0 mmol L-1. The humic acid elimination

was constrained by the addition of Tertiary butanol,

as shown in the gure, which decreased from 16.5

to 11.5 % with the addition of Tertiary butanol and

increased from 0.05 to 0.5 mol L-1.

According to its testimony, hydroxyl radical may

Anal. Methods Environ. Chem. J. 5 (3) (2022) 5-18

Fig. 3. Common anions’ effects on the elimination of humic acid in UV/SPB process

be the primary oxidizing agent in the symbiotic

system. After the addition of Tertiary butanol, the

removal of humic acid was not entirely inhibited,

which may be because the HO2 generated by

the breakdown of hydrogen peroxide (H2O2)

could likewise produce other activated particles,

including superoxide anion radicals (O2

.-) and

singlet oxygen (1O2) (Equation 18-22) [37,38],

which also have some oxidation ability and cannot

be entirely repressed by Tertiary butanol.

H2O2 2.OH

(Eq.18)

OH + H2O2 HO2

. + H2O

(Eq.19)

HO2

. O2

.- + H+

(Eq.20)

OH + O2

.- 1O2 + OH-

(Eq.21)

2H+ + O2

.- H2O2 + 1O2

(Eq.22)

3.2.2.Mechanism of humic acid degradation

The humic acid molecule structure changes may

be reected in the absorbance ratios [39]. Figure

5a depicts the development of these ratios in the

UV/SPB mechanism. The value of absorbance

ratio (253/203) declined from 0.98 to 0.44 with

a rise in reaction time, showing the durability of

functional groups (such as carboxyl [-COOH] and

carbonyl groups [-C=O]) in humic acid aromatic

structure gradually decreased. The absorbance

ratio (250/365) increased from 2.42 to 3.20, which

indicated that the humic acid molecular weight had

been reduced. The humic acid chromophore was

damaged by the absorbance ratio (254/436) rising

from 4.63 to 5.60. The absorbance ratio (465/665)

dropped from 3.5 to 1.0, demonstrating the loss of

aromaticity in humic acid.

The humic acid molecule’s structural differences

can also be seen in the UV-visible absorption

spectra. Figure 5b depicts the evolution of the

humic acid absorption spectrum in the UV/SPB

process over time. Implies that hydroxyl radical

produced in the UV/SPB process damaged the

chromophore groups and double bond structure

(C=C) of humic acid, as well as oxidizing the

UV/SPB process for removing humic acid in water Ahmed Jaber Ibrahim

Fig. 4. Tertiary butanol addition’s effect on humic acid removal

unsaturated ketone, the absorption edge of humic

acid at 200-250 nm, becomes weaker with time.

Additionally, the absorption edge shifted to the

region of short wavelengths, a phenomenon known

as blue shift. This proved that the carbon atom

substitution process took place in the carbonylic

group (C=O) of the humic acid chromophore [40].

Linearly expanded quinone groups and unsaturated

carbons make up humic acid and fulvic acid. When

specic substituent groups were used to replace the

carbon atom of a chromophore, such as a carbonyl

group (C=O), the absorption edge would shift to

a low amplitude. In general, specic ultraviolet

absorbances (SUVA) (254, 280, 365, and 436)

were chosen to describe the mineralization and

decomposition of natural organic matter. Where

SUVA-365 nm denotes the molecular volume,

SUVA-436 nm denotes the chromophore situation

in natural organic matter, SUVA-280 nm denotes

the stability of the aromatic system, and SUVA-254

nm denotes the molar mass [39].

After one hour of UV/SPB treatment, Figure 5c

demonstrates that the SUVA-254 and SUVA-

280 values decreased with time, indicating that

the molar mass of organic compounds decreased

and the basic aromatic framework was destroyed.

The decrease in SUVA-365 showed that as

the process developed, the volume of organic

molecules dropped. The lowering value of SUVA-

436 demonstrated that different oxidizing agents

destroyed the functional groups and chromophores.

Additionally, the total organic carbon (TOC) in the

process decreased from 7.139 to 2.440 mg L-1 and

the mineralization efciency increased to 65.81 %,

showing that the majority of humic acid had been

converted into water (H2O) and carbon dioxide

(CO2). UV spectrum and total organic carbon

ndings demonstrated that the UV/SPB symbiotic

therapy could successfully break down the intricate

chemical composition of humic acid.

Figure 6 displays the outcomes of further

investigating the humic acid degradation process

in the UV/SPB process using 3D-EEM. The

intricacy of the spectral reaction and the scanning

sample led to the division of the scanning spectrum

into ve sections. According to the structure

of heterocyclic amino acids in natural organic

matter, the I and II range can indicate aromatic

proteins in organic molecules [40]. The III region

in the humus structure denotes fulminate-like

compounds connected to hydroxyl (-OH) and

carboxyl (-COOH) groups. Region IV’s coverage

area reects the tiny molecular structure of organic

materials [35]. A humic-like uorescence is shown

by the V area. The uorescence density of the ve

locations whole decreased and slowly vanished

from 0 to 15 minutes (Fig. 6a and 6b) and 1 hour

(Fig. 6c), moreover demonstrating that the humic

acid molecular formula was broken down and

mineralized in this cooperative system.

Anal. Methods Environ. Chem. J. 5 (3) (2022) 5-18

Fig. 5. (a)Ultraviolet absorption level, (b) Ultraviolet-visible spectrum,

UV/SPB process for removing humic acid in water Ahmed Jaber Ibrahim

4. Conclusions

The UV/SPB synergistic technique was developed

in this work to eliminate humic acid from water,

and the experimental ndings showed that the

procedure could efciently degrade humic acid.

The humic acid elimination effectiveness was 88.83

% after 1 hour of therapy under the experimental

parameters of 10 mg L-1 humic acid concentration,

1 mmol L-1 Sodium perborate dose, and initial

pH 3. When compared to DI (deionized water),

the humic acid was eliminated far less effectively

In tap and lakes water. The anion effect studies

proved that, aside from SO4

-2, Cl-, and H2PO4

-. the

carbonate anion (CO3

-2), bicarbonate anion (HCO3

), and nitrate anion (NO3

-) exhibited varying

degrees of humic acid elimination inhibition.

By using masking tests, it was determined that

the primary chemical responsible for removing

humic acid was the hydroxyl radical produced

by Sodium perborate activation. Results from

the UV-vis spectrum, absorbance ratio, specic

UV absorbance (SUVA), and 3D-EEM together

demonstrated that the symbiotic mechanism could

decompose and mineralize humic acid in water

effectively.

5. Acknowledgements

This research is supported by the Physical Chemistry

Lab., Chemist Department, College of Education

for Pure Science (Ibn-al Haitham), University of

Baghdad.

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Anal. Methods Environ. Chem. J. 5 (3) (2022) 5-18

Anal. Methods Environ. Chem. J. 5 (3) (2022) 19-30

Research Article, Issue 3

Analytical Methods in Environmental Chemistry Journal

Journal home page: www.amecj.com/ir

AMECJ

A rapid removal of xylene from air based on nano-activated

carbon in the dynamic and static systems and compared to

commercial activated carbon before determination by gas

chromatography

Mostafa Jafarizaveha, Akram Tabrizia and Farideh Golbabaei b,*

a MSc. of Occupational Health Engineering, lecturer, Health Faculty, Gonabad University of Medical Sciences, Gonabad, Iran

b,* Professor of Occupational Health Engineering, Department of Occupational Health, Faculty of Health, Tehran University

of Medical Sciences, Tehran, Iran

ABSTRACT

As main air pollutants, volatile organic compounds (VOCs) must be

paid special attention. In this study, the removal efciency of xylene

from the air was investigated by nano-activated carbons (NACs) as

an efcient adsorbent and compared to commercial activated carbons

(ACs). In the chamber, the xylene vapor in pure air was generated,

stored in the airbag (5 Li), and moved to adsorbents. Then, the xylene

vapor was absorbed on the NAC/AC adsorbents and desorbed from

it by a heat accessory. The efciency of xylene removal with NACs

and ACs was investigated in the dynamic and static systems based on

100-700 mg L-1 of xylene, ow rates of 100 ml min-1, and 100 mg of

adsorbent at a humidity of 32% (25°C). Xylene concentrations were

determined by gas chromatography equipped with a ame ionization

detector (GC-FID). In the batch system, the maximum absorption

capacity for NACs and ACs was obtained at 205.2 mg g-1 and 116.8

mg g-1, respectively. The mean adsorption efciency for NACs and

ACs adsorbents was obtained at 98.5% and 76.55%, respectively. The

RSD% for NACs ranged between 1.1-2.5% in optimized conditions.

The characterizations of the NACs adsorbent showed that the

particle-size range was between 35-100 nm. The results showed that

the adsorption efciency of NACs for removing xylene from the air

was achieved more than ACs. The GC-MS validated the proposed

procedure in real air samples.

Keywords:

Xylene,

Adsorption,

Air,

Nano activated carbon,

Dynamic system,

Gas chromatography

ARTICLE INFO:

Received 5 May 2022

Revised form 12 Jul 2022

Accepted 22 Aug 2022

Available online 28 Sep 2022

*Corresponding Author: Farideh Golbabaei

Email: fgolbabaei@sina.tums.ac.ir

https://doi.org/10.24200/amecj.v5.i03.196

1. Introduction

Xylene is a colorless, aromatic hydrocarbon with

a sweet taste that is easily ammable. Xylene is

naturally present in petroleum and coal, and as

a result of forest res, it’s produced some of it.

Xylene is a toxic one-ring aromatic compound

that its release in the air can have a signicant

effect on the health and well-being of humans and

the quality of the air. The permissible exposure

limit (PEL or OSHA PEL) for xylene is 100

ppm in the air [1]. One of the main concerns of

industrial health experts is the control of volatile

organic compounds such as xylene. Activated

carbons are broadly dened to include the range

of amorphous carbon-based materials and have

a high degree of porosity with an extended

surface area[2]. Recently, the removal of organic

------------------------

compounds from the air by various processes

such as adsorption, bioltration and oxidation,

has been widely studied. Gholamreza Mousavi et

al showed that the xylene and other contaminated

air such as benzene were removed from the air

by a catalytic ozonation process. This study aims

to evaluate the efciency of activated carbon

based on ozone (catalytic ozonation) to remove

different concentrations of xylene. The results

indicated that the efciency of catalytic ozonation

for removing xylene in the air was higher than

single adsorption by AC [3]. In another study,

the effect of retention time, ozone dose and

relative humidity on the efciency of the catalytic

ozonation process in the removal of xylene from

contaminated air were studied by Gholamreza

Mousavi et al. They showed that the adsorption

capacity of the AC adsorbent improved with

the increase of inlet ozone dose as well as gas

ow rate[3]. So far, a wide range of adsorbents

has been used to separate various compounds

from the air. These adsorbents differ in physical

and chemical characteristics, such as the shape

and size of the cavity, surface area, cavity

volume, and surface activity. The superiority of

nanoadsorbents over previous adsorbents is due

to the nanometric scale, which causes tremendous

changes in their physical and chemical properties.

Other factors affecting the adsorption of analytes

(BTEX) are the much number of adsorption

sites and the extreme facilitation of molecular

interactions in nanoadsorbents. Bin Gao et al

reported developments of VOCs adsorption

onto a variety of engineered carbonaceous

adsorbents, including activated carbon, biochar,

activated carbon ber, carbon nanotube (CNTs),

graphene (NG/NGO) and its derivatives (IL-

NG), carbon-silica composites (CSC), ordered

mesoporous carbon(OMC), etc. The key factors

that inuence VOC adsorption are analyzed with

a focus on the physiochemical characteristics

of adsorbents, properties of adsorbates, and the

adsorption conditions[4]. Hamidreza Pourzamani

et al investigated the adsorption capacity of

nanoadsorbents to remove benzene and xylene

from aqueous solutions. In this study, single-

walled carbon nanotubes (SWCNTs), multi-

walled carbon nanotubes (MWCNTs), and hybrid

carbon nanotubes (HCNTs) were used. This study

showed that the efciency of nanoadsorbents

was signicant in removing xylene from the

air [5]. In another study, the removal of Ortho,

Meta, and para-xylene from the air samples

was carried out on an oxidized carbon nanotube

cartridge as an adsorbent by Le Huu Quynh Anh

et al. In this study, the oxidized carbon nanotube

with carbonyl groups signicantly increased

the adsorption capacity of xylene isomers[6].

In another study by Lu et al, the multi-walled

carbon nanotubes were oxidized with sodium

hypochlorite and used to remove ethyl benzene

and para-xylene from aqueous solutions and

signicantly improved the removal of benzene

and para-xylene[7]. Also, Golbabaei et al showed

that nano-activated carbon adsorbent has a

higher adsorption capacity for xylene removal

compared to commercial activated carbon in

the static state[8]. The adsorption of BTEX on

carbon nanotube cartridges from air samples

was reported by Le et al and the results showed

that the CNTs had high potential for BTEX

adsorption due to their microporous structure

and high surface area[9]. They showed that the

oxidized CNTs with carbonyl groups increased its

adsorption capacity for these isomers [6]. Also,

Shahi Ahangar showed that the photocatalytic

removal efciency in the concentrations of 50,

100, and 300 ppm was equal to 87.8%, 98.9%, and

90.8%, respectively [10]. Many researchers used

different pilot and nanoadsorbents (Ni-MWCNTs,

GQDs, NGO, NG, MSN, ILs, Silica) to remove

hazardous pollutants such as toluene, ethyl

benzene, mercury, benzene, dust, and hydrogen

sulde from the air [4,11-20]. Finally, according to

those mentioned above and the high efciency of

nanoadsorbents compared to other adsorbents in

the removal of different materials in the previous

studies, a comparison study for adsorption of

xylene from the air between commercial activated

carbon absorbent and Nano carbon adsorbent was

Anal. Methods Environ. Chem. J. 5 (3) (2022) 19-30

obtained to survey the effect of nanoadsorbent in

the removal of xylene from the air. The previous

studies for removing BTEX from the air reported

a low efciency in the air ambient.

In this study, NACs were used as adsorbent to

remove xylene vapor from the air and compared to

ACs (NIOSH adsorbent). All effective parameters

were optimized. The xylene in pure air was

generated in the chamber of pilot for the dynamic

process. Also, the effect of temperature on the

desorption/desorption of xylene and reusability

of NACs or ACs adsorbents was studied. The

retention time of nano-activated carbon was also

studied and its efciency was calculated over

different days (inter-day and intra-day).

2. Experimental

In this experimental-analytical study, the feasibility

of replacing activated carbon with nano-activated

carbon for removing xylene vapors from the air

was studied. The study was done according to the

following steps.

2.1. Instrumental and Reagents

In this study, Gas chromatography equipped with

a ame ionization detector was used (Varian 3800,

CP7996 with a length of 25 m and a diameter of

0.25 mm). The FID detector was chosen for xylene

analysis in gas/liquid. Before injection, the slide

the plunger carrier down until it is completely

over the syringe plunger, and tighten the plunger

thumb screw nger-tight. The injector temperature

was adjusted to 200°C. The column temperature

reached from 35°C to 90°C with the speed of

20°C per minute, and the split ratio was adjusted

from 2 to 1. The detector temperature tuned at

220°C. Hydrogen gas as a carrier gas was used

at a ow rate of 30 ml min-1. A Hamilton syringe

was used for sample injection into the injector.

Minimum and maximum pressures in psi for inlets

and detectors tuned at the bulkhead tting at the

back of the gas chromatograph (100 psi). Finally,

according to the peak areas of injecting of different

xylene concentration to the GC-FID, a calibration

curve was drawn (Fig.1). Agilent 5977B single

quadrupole GC/MS based on cost-effective solution

including the High-Efciency Source (HES) for

the most challenging detection limit samples

was used for the xylene determination and the

validation of procedure. Chemicals were acquired

from Sigma Aldrich Germany. The mixed xylene

(Catalogue Number: 108633, CAS N:1330-20-7,

ACS, 99.5% purity) and para-xylene (Catalogue

Number: 108684, CAS N:106-42-3, ACS, 99.7%)

was procured from Merck. The standard solutions

of xylene were made based on the procedure.In

this study, the activated carbon (ACs) and Nano-

activated carbon adsorbents (NACs) were prepared

from Iranian Research Institute of the Petroleum

Industry (RIPI, size <100 nm).

Removal of xylene by Nano Activated Carbon and Activated Carbon Mostafa Jafarizaveh et al

Fig.1. Peak area of GC-FID for species of xylene

2.2. Characterizations

The nano-activated carbon specication

was investigated by Transmission Electron

Microscopy (TEM), Electron Microscopy

Scanning (SEM), and X-Ray Diffraction (XRD)

at the Iranian Research Institute of the Petroleum

Industry (RIPI). X-ray diffractions (PW 1840,

Phillips, Netherland) based on radiation source

of Cu-Kα. The morphologies of the NACs were

achieved by scanning electron microscopy (SEM)

and transmission electron microscopy(TEM),

respectively (PW3710, CM30, Philips,

Netherland). SEM and TEM of NACs showed

Nano size below 100 nm.

2.3. Absorption procedure

In this study, according to the NIOSH method

[21], various concentrations of xylene (purchased

from Merck Company) were prepared in a range

of 10 to 300 mg L-1 in sampling bags (Tedlar).

Then, using a syringe, 400 microliters from the air

existent in the sample bags were taken. In dynamic

procedure,the different xylene concentration in

pure air was made in the chamber of pilot. (Fig.2).

The standard solution of xylene vapored in the

chamber, mixed with pure air, and moved to a

PVC storage bag (1-5 Li) at 25oC. GC-FID has

measured the certied reference gas of xylene.

Then the xylene gas moved to NACs sorbent and

AC with a ow rate from 100 mL up to 300 mL

per min. After xylene absorption on the NACs/

ACs adsorbents, the xylene was released from the

adsorbent by heating up to 150oC. Then xylene

concentration was determined by GC-FID. In the

static system, the absorption xylene based on AC

and NACs was achieved by a closed GC vial. In

the static state, various concentrations of xylene

were injected into the vial containing 5.0 mg

adsorbent. Then 400 µl of air from the vial was

injected into the GC, and the adsorption capacity

of the NACs/ACs adsorbents was calculated

according to Equation 1.

(Eq. 1)

Fig.2. A schematic of the dynamic absorption system

Anal. Methods Environ. Chem. J. 5 (3) (2022) 19-30

3. Results and Discussion

3.1. Absorption efciency and the effect of

various factors on NACs

In this study, the different concentrations of

50, 200, 450, and 700 mg L-1 of xylene were

injected by syringe into the chamber (Impinger)

in presence of pure air. Then, the micro personal

sampling pump (SKC, 20-300 ml min-1) in

different flows (100, 200, and 300 ml min-

1) passed the air containing xylene from the

impinger into a sample bag (1 or 3 liters). In

this experiment, at the beginning of every test,

the impinger was heated to warm the air inside,

and xylene was steamed completely. Finally,

after filling the sample bag, the air inside it was

taken by GC gas syringe and injected into GC-

FID, and then, the results were analyzed. After

assuring the mixing of xylene with inlet air into

the designed pilot, the adsorbent was placed

after the sampling bag. The amount of weight

of adsorbent was 100, 150, and 200 mg. During

this experiment, the adsorption of various

concentrations of xylene in different air flows and

amounts of adsorbent mass were investigated.

The experiments were carried out at constant

moisture and an ambient temperature (25 °C).

It should be noted that these experiments were

carried out for two activated carbon and Nano

activated carbon, and adsorption efficiency was

calculated after a sampling time of 30 minutes

(Equation 2). Each experiment was repeated five

times, and the efficiency was obtained below

Equation 2.

Efficiency (%) = (Ci - Cf) / (Ci) × 100

(Eq. 2)

Ci: initial xylene concentration and Cf: xylene

concentration after passing from the adsorbent.

3.2. The storage stability of NACs

In this stage, to determine xylene adsorbed

Nano-activated carbon, the 300 mg L-1 of xylene

was passed on absorbent (100 mg) with a flow

of 100 ml min-1. After the adsorption of xylene

on NACs or ACs, two ends of the absorbent tube

were sealed with paraffin and stored at 0 °C, and

the absorbent was analyzed at different times (in

terms of days), and the efficiency was calculated

according to Equation 3

Removal Efficiency (RE) = Af / Ai × 100

(Eq. 3)

(Af= Final analysis for xylene concentration

adsorbed on adsorbent after distinct duration

Ai: initial analysis for xylene concentration

adsorbed on adsorbent).

3.3. Repeatability of NACs

Nano-activated carbon (NACs) recovery and its

reusability were studied in this study. For this

purpose, the nano activated carbon adsorbent

was used in the dynamic system. The adsorbent’s

efficiency was obtained in a concentration of

300 mg L-1 from xylene in a flow rate of 100

ml min-1 and 100 mg of adsorbent. After xylene

adsorption on NACs adsorbent, the xylene

desorbed from NACs by the thermal accessory.

The results showed that the recovery decreased

after 16 times of adsorption/desorption. So, 16

times was considered as the number of reusability

of adsorbent. The analysis for NACs or ACs was

done three times (Mean of three determinations

of samples ± confidence interval; P = 0.95, n

=10). In this study, the mean values of the results

are presented.

3.4. Data analysis and images

To analyze the data and compare the efficiency

of various adsorbents for the removal of xylene,

the SPSS software version 16 was used. Nano-

activated carbon was analyzed utilizing TEM,

XRD and SEM. The XRD, SEM, and TEM of

activated carbon (ACs) and Nano activated

carbon (NACs) are shown in Fig. 3a-e. The

particle size of Nano-activated carbon was

obtained below 100 nm by SEM and 30 nm

by TEM. Also, XRD images showed a cubic

structure of Nano activated carbon and activated

carbon.

Removal of xylene by Nano Activated Carbon and Activated Carbon Mostafa Jafarizaveh et al

Fig.3a. SEM of activated carbon (ACs)

Fig.3c. TEM of activated carbon (ACs)

Fig.3b. SEM of Nanoactivated carbon (NACs)

Fig.3d. TEM of Nanoactivated carbon (NACs)

Fig.3e. XRD of activated carbon (ACs) and Nano activated carbon (NACs)

Anal. Methods Environ. Chem. J. 5 (3) (2022) 19-30

3.5. Adsorption Performance

The descriptive analysis of the adsorption

efciency (%) for NACs and AC is shown in

Table 1. As can be seen, the average value of the

adsorption efciency of NACs is higher than AC

(respectively 98.48 and 76.55). The statistical

analysis of the results showed that the difference

between the mean efciency in Nano activated

carbon and activated carbon was insignicant.

(P-value =0.474). Linear regression was used to

analyze the variables. In this analysis, the linear

relationship between the dependent variable

(adsorption efciency, %) and independent variables

(x1: xylene concentration, mg L-1), (X2: air ow

rate, ml min-1) and (x3: adsorbent mass, mg) was

investigated. The multi-linear regression equation

was obtained as Equation 4 (RAC: Activated carbon

efciency, RNAC: Nano carbon Active Absorbance

Adsorption Efciency).

RCA=75.598-0.027x1-0.042x2+0.087x3

RNCA=98.737-0.024x1-0.057x2+0.09x3

(Eq. 4)

Regarding the nano activated carbon adsorbent,

the value of R2 was 0.9895 in the activated carbon

adsorbent equal to 0.9524. The correlation between

the adsorption efciency of NAC and ACs obtained

experimentally. The linear regression equation

obtained from the adsorptions results of xylene

by nano activated carbon and activated carbon

adsorbents which were shown that there was a high

correlation between them (correlation coefcient:

0.833) .

3.6. Effect of xylene concentration

In this study, the adsorption efciency of xylene

by NAC and ACs adsorbents in various xylene

concentrations at optimized conditions such as the

ow rate of 100 ml min-1 and 200 mg of absorbance

was evaluated. First, the adsorption efciency was

constant and then, decreased by increasing the

xylene concentration. The adsorption efciency

in the activated carbon adsorbent (ACs) was

decreased signicantly more than NACs adsorbent.

At concentrations of 50, 100, 450 and 700 mg L-1,

the removal efciency of NACs and ACs for 10

analyses was obtained (99.8%, 99.4%, 97.6% and

95.8%) and (77.4%, 75.9%, 69.2% and 60.1%),

respectively.

3.7. Effect of ow rate

According to the results, the adsorption efciency

was decreased with an increasing ow rate. The

effect of ow rate on activated carbon efciency is

higher than Nano activated carbon. At ow rates of

100, 200, and 300 ml min-1 with 200 mg adsorbents

and xylene concentration of 100-200 mg L-1, the

removal efciency of nano-activated carbon was

equal to 98.5%, 94.3%, and 90.6%, respectively

and for ACs was achieved 76.5%, 67.3% and

52.6%, respectively (Fig.4).

Table 1. Descriptive and analytical analysis of adsorbent efciency of Nano activated carbon

and activated carbon (P-value=0.474)

Adsorbent type Number AEA SD SE

CI( 95%)

Lower

limit

Upper

limit

NACs 36 98.48 10.27 1.7 97.2 99.8

AC 36 76.55 10.03 1.67 67.4 85.7

Average 72 87.49 10.08 1.18 82.3 92.75

AEA: Adsorption Efciency Average

SD: Standard Deviation

SE: Standard Error

CI: Condence Interval

Removal of xylene by Nano Activated Carbon and Activated Carbon Mostafa Jafarizaveh et al

3.8. Effect of adsorbent mass

According to the result, by increasing adsorbent,

the removal efciency of xylene from air increased

and then constant. At the adsorbent mass of 100,

150 and 200 mg and concentration of 200 mg

L-1 and ow rate of 100 ml min-1, the efciency

of Nano activated carbon was 96%, 97.5%, and

98.5%, respectively. So, 100 mg of NAC was

used as optimum amount of adsorbent. (Fig.5)

3.9. The effect of ow rate based on the amount

of adsorbent

Figure 6 shows the combined effect of ow rate and

the amount of adsorbent mass on the adsorption

efciency of nano activated carbon at various

concentrations. As shown in Figures 5 and 6,

by increasing amount of adsorbent and decreasing

airow rate, the adsorption efciencies were

increased.

Fig.4. Effect of owrate on removal efciency of xylene by NACs and ACs adsorbents

Fig.5. Effect of amount of NACs and ACs adsorbents on removal efciency of xylene

Anal. Methods Environ. Chem. J. 5 (3) (2022) 19-30

3.10. The effect of retention time

The effect of retention time of NAC on the

xylene removal from air was investigated. Table 2

shows the xylene values added to the NACs and

ACs adsorbents after passing pure air containing

xylene vapor over it at a ow rate of 100 ml min-

1 on different days (1, 3, 7, and 21 days). Then,

the removal efciency of the NACs and ACs

adsorbents was calculated. The results showed that

the retention time on nano-activated carbon was

signicant.

3.11. Effect of reusing and storage of adsorbent

By thermal accessory, the adsorbent recovered

for 30 minutes. After 16 times of adsorption/

desertion, the adsorbent efciency was from

95.9%-99.3% for primary absorbent. After storing

the closed original adsorbent in the refrigerator,

it reached 94.5-96.1%. So, it is desirable with

good recovery for removal of xylene by NACs in

optimized conditions for 10 days storage in the

refrigerator (- 40C). After 10 days, the recovery

decreased.

Removal of xylene by Nano Activated Carbon and Activated Carbon Mostafa Jafarizaveh et al

Fig. 6. Combined Effect of airow and adsorbent mass on the adsorption efciency of NACs

Table 2. Results of the retention time for xylene removal from air by NACs (P-value: 0.462-0.513)

(%) EfciencyXM3

RTFRXM2

AMXMRow

99.3108.151100108.21008.61

99.2108.063100108.121008.62

98.6108.197100108.31008.63

98.3107.8221100107.951008.64

XM2: xylene value (mg L-1 ) + adsorbent mass (mg)

XM3: The xylene value(mg L-1 ) + adsorbent mass after retention time (days)

FR: Flow rate (ml min-1)

RT: Retention time (days)

AM: adsorbent mass (mg)

XM: Xylene value (mg L-1 )

3.12. Discussion

Activated carbon is one of the essential adsorbents for

removing volatile organic matter. In this study, nano-

carbon adsorbent’s efciency for removing xylene

from air compared to activated carbon and other

carbon structures. Due to results and comparison of

efciency between NAC and AC adsorbents, NAC

adsorbent had better performance and capacity than

activated carbon for removing xylene from the air

in the optimized conditions (xylene concentration,

owrate, and amount of adsorbent). The average

adsorption efciency of the NAC adsorbent was

higher than activated carbon adsorbent in the same

conditions (NAC:98.5% and AC:76.5%). The

results showed that the difference in efciency was

not statistically signicant (p-Value = 0.474). Due to

previous studies, the efciency of nano absorbents

such as CNTs, GO, NG, and CQDs was higher

than activated carbon. Golbabaei et al showed that

the adsorption capacity of nano-activated carbon

for xylene is higher than the activated carbon in

the static state. There is a signicant difference

between the adsorption capacity and recovery of

the two adsorbents. In another study by Golbabei

et al, the results showed that the Nanographene had

a higher adsorption capacity than nano graphene

oxide and activated carbon adsorbents for removing

xylene from the air. Also, they showed that the

adsorption efciency of nano adsorbents such

as NAC, NG, NGO, and CNTs was higher than

AC for removing xylene from the air [22]. Tanju

Karanl et al reported the adsorption of volatile

organic pollutants by Nanographene sheet, which

was compared to the carbon nanotube, activated

carbon, and Nanographene. They introduced these

alternative adsorbents to remove industrial organic

compounds from water. This study also shows the

high performance of the Nano adsorbent [23]. The

results showed that increasing the air ow rate and

the xylene concentration decreased the removal

efciency. On the other hand, the removal efciency

increased by adding the amount of adsorbents such

as NAC or AC. This is due to an increase in retention

time and available adsorption sites. Also, the results

showed that a ow rate had a more signicant effect

on nano-activated carbon than activated carbon.

This effect of the airow rate caused no signicant

difference between the adsorption efciency of the

activated carbon and the nano-activated carbon.

In fact, the study shows that low ow rates give

better adsorption because the increase in ow rate

actually creates a turbulent stream and the xylene

molecules do not have enough time to adsorb onto

the adsorbent. The results of ow rate and amount

of adsorbent in the present study were similar to

the results of Asilian et al. Asilian et al showed that

the absorption capacity of xylene for zeolite was

decreased up to 1.69 mg g-1 by increasing ow rate.

Also, in a high ow rate, the time of failure and

saturation time decreased in zeolite adsorbent [24].

Asilian also reported that increasing the amount

of adsorbent cause to increase the adsorption

efciency. In fact, in this study, adsorption efciency

in low owrate is was excellent and consistent [24].

Lu et al showed that the carbon nanotube oxidized

with sodium hypochlorite had a higher BTEX

adsorption than carbon nanotube and granular

activated carbon. They showed that the physical

and chemical properties of carbon nanotubes

such as purity, structural and surface nature after

oxidation were signicantly improved, which led to

a signicant increase in BTEX adsorption capacity.

Also, Shirkhanloo et al reported that the adsorption

capacity of ionic liquid modied on nanographene

caused to increase in the toluene removal from the air.

The absorption capacity of toluene for IL-NGO was

obtained at 126 mg g-1 which shows the remarkable

favorite efcacy of nanoadsorbent for removing of

volatile organic compounds. The modication of

nanoadsorbent increased the potential of toluene

removal [25]. In the present study, according to the

results of experiments in different conditions, the

nano-activated carbon showed a higher removal

efciency than activated carbon and competed with

the IL/NGO or IL/CNTs. One of the critical factors

for absorbents is the ability to recycle them. Nano

adsorbents are the most economical and recyclable.

By the proposed procedure, the results showed that

the nano-activated carbon can also be recovered by

heating and can be reused many times.

Anal. Methods Environ. Chem. J. 5 (3) (2022) 19-30

Removal of xylene by Nano Activated Carbon and Activated Carbon Mostafa Jafarizaveh et al

4. Conclusion

During the review of previous studies, it has been

found that this study is the only one conducted

to evaluate the efciency of nano activated

carbon adsorbent in removing xylene. This study

showed that the nano activated carbon adsorption

efciency (98.5%) was somewhat higher than

the activated carbon (76.5%), this difference was

statistically signicant. The absorption capacities

(AC) for the NACs and ACs adsorbents ranged

from 187.6-245.2 mg g-1 and 89.7-132.4 mg g-1,

respectively (n=10, m=100 mg). According to the

results, both absorbents have the potential to be

used for removing xylene from the air with favorite

efciency and capacity. As a suggestion, the NACs

as a novel adsorbent can be used optimally and

more studies are needed in this regard.

5. Acknowledgment

This study has been funded and supported by the

Tehran University of Medical Sciences and the

research ethics code is IR.TUMS.REC.1394.176.

The authors would like to thank the Tehran

Research Institute of Petroleum Industry and

authorities of the Occupational Health Laboratory

of Tehran University of Medical Sciences for their

contribution.

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Anal. Methods Environ. Chem. J. 5 (3) (2022) 31-39

Research Article, Issue 3

Analytical Methods in Environmental Chemistry Journal

Journal home page: www.amecj.com/ir

AMECJ

Catalytic ozonation process using ZnO/Fe2O3 nanocomposite

for efcient removal of captopril from aqueous solution

Maryam Dolatabadi a, b, Ruhollah Akbarpour c, Saeid Ahmadzadeh d, e*

a Student Research Committee, Kerman University of Medical Sciences, Kerman, Iran.

b Environmental Science and Technology Research Center, Department of Environmental Health Engineering, School of

Public Health, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.

c MSc student in Environmental Engineering, Islamic Azad University, Estahban branch, Estahban, Iran.

d Pharmaceutics Research Center, Institute of Neuropharmacology, Kerman University of Medical Sciences, Kerman, Iran.

e Pharmaceutical Sciences and Cosmetic Products Research Center, Kerman University of Medical Sciences, Kerman, Iran

ABSTRACT

The presence of pharmaceutical compounds in aqueous media, even

in low concentrations, has caused adverse effects on human, animal,

and environmental health. Captopril is a widely used pharmaceutical

compound detected in the environment at different concentrations.

Because of the concern and problems caused by the presence of

captopril in water and the aquatic ecosystem, it appears necessary

to remove it from the environment. The current study investigated

captopril removal by a catalytic ozonation process using ZnO/Fe2O3

nanocomposite as a low-cost catalyst. The effects of variables such

as ZnO/Fe2O3 nanocomposite dosage (0.5-2.5 g L-1), solution pH (3-

11), initial captopril concentration (10-70 mg L-1), and ozone dosage

(0.2-1.5 mg min-1) on captopril removal were investigated. The

removal captopril of 99.4% was obtained in the optimum condition,

including ZnO/Fe2O3 nanocomposite dosage of 2.0 g L-1, solution pH

of 5.0, initial captopril concentration of 40 mg L-1, and ozone dosage

of 0.5 mg min-1. The ZnO/Fe2O3 nanocomposite as a catalyst was a

critical component in the catalytic ozonation process. According to

the obtained results, the catalytic ozonation process in the presence of

ZnO/Fe2O3 nanocomposite has high efciency in removing captopril

from water sources.

Keywords:

Captopril,

Catalytic ozonation,

ZnO/Fe2O3 nanocomposite,

Removal,

Aqueous solution

ARTICLE INFO:

Received 27 Apr 2022

Revised form 23 Jun 2022

Accepted 15 Jul 2022

Available online 28 Sep 2022

*Corresponding Author: Saeid Ahmadzadeh

Email: saeid.ahmadzadeh@kmu.ac.ir

https://doi.org/10.24200/amecj.v5.i03.197

1. Introduction

Recently, the attention of many researchers

working in the eld of water and wastewater

treatment has focused on the removal of

pharmaceutical compounds as a new group of

emerging pollutants [1]. After humans and animals

consume pharmaceutical compounds, part of

them in their unmetabolized and metabolized

form is excreted from the body and enters the

environment [2]. Captopril is a commonly used

pharmaceutical compound prescribed to reduce

high blood pressure, treat heart failure, protect

the heart and blood vessels against damage and

heart attack, and protect the kidneys in diabetic

patients [3, 4]. Captopril is a potent, competitive

inhibitor of the angiotensin-converting enzyme, the

enzyme responsible for converting angiotensin I to

angiotensin II. Angiotensin II is a potent mediator

that causes the narrowing of blood vessels and

retention of sodium and water in the body [5].

Captopril has been detected in various

environments such as water and soil). The captopril

concentration in the environment causes dizziness,

------------------------

32 Anal. Methods Environ. Chem. J. 5 (3) (2022) 31-39

cough, hyperkalemia, impotence, nocturnal

enuresis, nausea, vomiting, diarrhea, insomnia,

Stevens-Johnson syndrome, gynecomastia,

thrombocytopenia, and angioedema. Considering

the problems caused by the presence of captopril

in the environment, removing captopril from

the aquatic environment is essential [3, 4].

Although conventional processes in water and

wastewater treatment can remove a part of

pharmaceutical compounds during the treatment

process, conventional treatment processes cannot

thoroughly remove these compounds, so we nally

need advanced oxidation processes to treat these

pollutants [6].

Ozonation technique is one of the advanced

oxidation processes in water and wastewater

treatment. Ozonation is used in water and

wastewater treatment for several purposes such as

disinfection, removal and control of taste, odor, and

color, oxidation of iron and manganese and other

mineral contaminants, algae control, improving the

coagulation process, and oxidation of persistent

organic contaminants [7, 8].

As a strong oxidant, Ozone molecules break down

recalcitrant and hazardous organic compounds into

smaller molecules [9, 10]. The ozonation reaction

is accomplished through two pathways (direct and

indirect). In the direct method, the ozone molecule

appears as an electron acceptor and thus oxidizes

the organic pollutants. Nevertheless, in the indirect

method, the ozone molecule is converted into a

radical (•OH) during chain reactions, which has a

higher oxidation potential than ozone. The indirect

method decomposes pollutants with incredible

speed and power [11, 12]. Ozone presents a

high reactivity mainly attributed to its electronic

conguration. It is a selective molecule that attacks

electron-rich functional groups like double bonds,

amines, and activated aromatic rings [13, 14]. In

recent years, heterogeneous catalytic ozonation

has received much attention in water treatment

due to its high oxidation potential. In the current

work, the effect of main operational variables,

including solution pH, catalyst dosage (ZnO/Fe2O3

nanocomposite), initial captopril concentration,

and reaction time was evaluated during the catalytic

ozonation for removal of captopril from aqueous

solution.

2. Material and methods

2.1. Chemical

Captopril (C9H15NO3S, CAS N: 62571-86-2) was

purchased from Darou Pakhsh Pharmaceutical

Company. Sodium chloride (NaCl, CAS Number:

7647-14-5; Molecular Weight: 58.44), sodium

hydroxide (NaOH, CAS 1310-73-2. Molecular

Weight 40.00), hydrochloric acid (HCl, reagent,

37%; CAS Number: 7647-01-0; EC Number: 231-

595-7), sodium thiosulfate (Na2S2O3, CAS Number:

7772-98-7; Molecular Weight: 158.11), ferric chloride

(FeCl3, CAS 7705-08-0, EC Number 231-729-4), zinc

oxide (ZnO, CAS 1314-13-2, Molecular Weight

81.39), acetonitrile anhydrous (CAS Number: 75-

05-8, Molecular Weight: 41.05) , triuoroacetic

(TFA, CAS 76-05-1, Molecular Weight 114.02), and

potassium iodide (KI, CAS 7681-11-0, Molecular

Weight 166.00), were obtained from Sigma,

Germany. All chemicals were of analytical reagent

grade.

2.2. Instrumental

The determination of captopril concentration

was analyzed using high-performance liquid

chromatography (HPLC) system (HPLC 862

Bar, Knauer Smartline, Germany). This system

consisted of a photodiode array (PDA) detector,

set at 282 nm, and a C18 column (RP-C18, 5 µm

4.6 ×150 mm) kept at 30°C, with an injection ow

rate of 1.2 mL min-1. The mobile phase solution

was applied using 15% acetonitrile and 85%

triuoroacetic/water acid (2% v/v) [16]. Digital PH

meter (meterohom 827 pH lab, Switzerland) was

used.

2.3. Preparation of the ZnO/Fe2O3 nanocomposite

In a theoretical procedure, 19.4 mg FeCl3 and

200 mg ZnO particles were added to 50 mL of

deionized water, and the mixture was dispersed at

100 °C for 12.0 h (Fig.1). After cooling to 20 °C, the

nanoparticles were separated using centrifugation

Removal of Captopril by ZnO/Fe2O3 Nanocomposite Maryam Dolatabadi et al

Fig.2. SEM images of the ZnO/Fe2O3 nanocomposite

Fig.1. Procedure for Preparation of the ZnO/Fe2O3 nanocomposite

and washed several times with ethanol and deionized

water. The ZnO/Fe2O3 nanocomposite was dried at

100°C for 3.0 h and then was used as the catalyst

in the ozonation process for the degradation of

captopril [15]. FE-SEM of nanoparticles of ZnO/

Fe2O3 nanocomposite showed in Figure 2.

2.4. Catalytic ozonation experiments

The catalytic ozonation of captopril was

performed in a 500 mL Pyrex reactor with 8.0

cm diameter and 12 cm high and equipped with a

magnetic stirrer at room temperature. Ozone was

generated from the air using an ozone generator

(ARDA, Model MOG+10) with an input rate of

5 g h-1. The reactor included an input/output port

for the ozone gas stream. Ozone was introduced

through a porous fritted diffuser that can produce

reasonably ne bubbles. The excess ozone at

the outlet was adsorbed by a sequential 2%

potassium iodide solution. The solution pH was

adjusted using NaOH or HCl in the catalytic

ozonation process. After performing the reaction

in each experimental run, 5 mL of sample was

34 Anal. Methods Environ. Chem. J. 5 (3) (2022) 31-39

100

010 20 30 40 50 60

Removal Efficiency (%)

Reaction time (min)

pH=3

pH=5

pH=7

pH=9

pH=11

taken and ltered by PTFE lters to analyze

for degradation efciency of captopril using

the catalytic ozonation process. Mechanism of

removal of captopril based on the ZnO/Fe2O3

nanocomposite by the catalytic ozonation which

was presented in Figure 3.

3. Results and discussion

3.1. Effect of solution pH

The effect of solution pH is one of the critical

parameters in the catalytic ozonation process for

removing contaminants. Therefore, in the present

study, the effect of solution pH was investigated in

the range of 3.0 to 11.0 for removal of captopril

from aqueous solution, in the constant condition,

including initial captopril concentration of 30 mg

L-1, ZnO/Fe2O3 nanocomposite dosage of 1.0 g L-1,

and ozone dosage of 0.5 mg min-1. The obtained

results are shown in Figure 4. According to the

achieved results, it was found that the removal

Fig.3. Mechanism of removal of captopril based on the catalytic ozonation

and the ZnO/Fe2O3 nanocomposite

Fig. 4. Effect of solution pH and reaction time for removal captopril using catalytic ozonation. Experimental

conditions: initial captopril concentration of 30 mg L-1, ZnO/Fe2O3 nanocomposite dosage of 1.0 g L-1, ozone

dosage of 0.5 mg min-1.

Removal of Captopril by ZnO/Fe2O3 Nanocomposite Maryam Dolatabadi et al

100

010 20 30 40 50 60

Removal Efficiency (%)

Reaction time (min)

Dose= 0.5 g/L

Dose= 1.0 g/L

Dose= 1.5 g/L

Dose= 2.0 g/L

Dose= 2.5 g/L

efciency of captopril decreased with the increase

of pH solution. As the pH value increased from 3

to 11, the removal efciency of captopril decreased

from 85.8% to 51.2% after 60 min. The removal

efciency in the acid conditions is better than in

alkali conditions because high pH in the solution

leads to the creation of more free radical scavengers

derived from the mineralization of organic material,

resulting in a decrease in the concentration of •OH.

Generally, ozone oxidation pathways include direct

oxidation by ozone molecules and radical oxidation

by •OH. Direct oxidation is more selective and

dominates under acidic conditions. While radical

oxidation is less selective and predominates under

primary conditions [17, 18]. Since the removal

efciency at a solution pH of 5 (82.6%) is very

close to the removal efciency at a solution pH of

3 (85.8%), due to the destructive effects of acidic

conditions, a pH of 5 was chosen as the optimal

solution pH in the catalytic ozonation process for

removal of captopril.

3.2. Effect of ZnO/Fe2O3 nanocomposite dosage

The effect of catalyst dosage (ZnO/Fe2O3

nanocomposite) on captopril removal in the

catalytic ozonation process was investigated in the

range of 0.50–2.5 g L-1. In the constant condition,

including solution pH of 5, initial captopril

concentration of 30 mg L-1, and ozone dosage of

0.5 mg min-1. According to the obtained results,

the captopril removal efciency increased with

increasing ZnO/Fe2O3 nanocomposite dosage.

As seen in Figure 5, the removal efciency of

captopril increased to 72.3%, 82.6%, 88.6%,

95.6%, and 98.2% when the catalyst dosage (ZnO/

Fe2O3 nanocomposite) was increased to 0.50, 1.0,

1.5, 2.0, and 2.5 g L-1, respectively. Nevertheless,

the captopril removal efciency at the catalyst

(ZnO/Fe2O3 nanocomposite) dosage of 2.0 g L-1 is

very close to 2.5 g L-1 (less than 3%). Therefore,

a catalyst dosage of 2.0 g L-1 was chosen as the

optimum catalyst dosage. The obtained results

illustrate that ZnO/Fe2O3 nanocomposites show

high performance on catalytic oxidation removal

of captopril. During catalytic ozonation, catalysts

can promote the ozonation process and generate

active free radicals. Consequently, enhancing

the degradation and mineralization of organic

contaminants [10, 14].

3.3. Effect of the initial captopril concentration

The effect of the initial concentration of captopril on

the removal efciency using the catalytic ozonation

process was investigated in the range from 10 to 70

mg L-1. In the stable condition, including solution

pH of 5, ZnO/Fe2O3 nanocomposite dosage of 2.0 g

L-1, and ozone dosage of 0.5 mg min-1. The results

are displayed in Figure 6. The removal efciency of

Fig. 5. Effect of ZnO/Fe2O3 nanocomposite dosage and reaction time for removal captopril

using catalytic ozonation. Experimental conditions: initial captopril concentration of 30 mg

L-1, solution pH of 5.0, ozone dosage of 0.5 mg min-1.

36 Anal. Methods Environ. Chem. J. 5 (3) (2022) 31-39

captopril indeed decreased with the increase of the

initial concentration. After 60 min of reaction time,

when the initial concentration of captopril increased

to 10, 30, 40, 50, and 70 mg L-1 removal efciency

reached 100.0%, 95.6%, 92.1%, 88.4%, and

73.9%, respectively. This phenomenon can be due

to, at constant conditions, the ozone concentration

in the reactor being constant, so the amount of •OH

in the reactor would be constant under the same

conditions. The high concentration of captopril

would consume more •OH, so the removal

efciency is reduced with the increase of the initial

concentration of contaminants [19, 20]. Due to the

captopril removal efciency at a concentration of

40 mg L-1 being a good performance (above 90%),

a captopril concentration of 40 mg L-1 was selected

as the optimum concentration.

3.4. Effect of ozone dosage

Figure 7 shows the removal efciency of captopril

under different ozone dosages. Various levels of

ozone dosage were set by adjusting the inlet gas

100

010 20 30 40 50 60

Removal Efficiency (%)

Reaction time (min)

0.2 mg/min

0.5 mg/min

1.0 mg/min

1.5 mg/min

100

010 20 30 40 50 60

Removal Efficiency (%)

Reaction time (min)

10 mg/L

30 mg/L

40 mg/L

50 mg/L

70 mg/L

Fig. 6. Effect of initial captopril concentration and reaction time for removal captopril using

catalytic ozonation. Experimental conditions: solution pH of 5.0, ZnO/Fe2O3 nanocomposite

dosage of 1.0 g L-1, ozone dosage of 0.5 mg min-1.

Fig. 7. Effect of ozone dosage and reaction time for removal captopril using catalytic ozonation. Experimental conditions:

solution pH of 5.0, ZnO/Fe2O3 nanocomposite dosage of 2.0 g L-1, initial captopril concentration of 40 mg L-1.

Removal of Captopril by ZnO/Fe2O3 Nanocomposite Maryam Dolatabadi et al

concentration. The ozone dosage effect in the

range of 0.2 to 1.5 mg min-1 was investigated in

constant conditions, including solution pH of 5,

ZnO/Fe2O3 nanocomposite dosage of 1.0 g L-1,

and initial captopril concentration of 40 mg L-1.

The experimental results are presented in Figure

4. According the results, the captopril removal

efciency increased to 75.0%, 92.1%, 99.4%, and

99.6% when the ozone dosage was increased to

0.2, 0.5, 1.0, and 1.5 mg min-1, respectively. More

than 99.4% of captopril is removed within 45

minutes when the ozone dosage is 1.0 mg min-1.

Further increase of ozone dosage (≥1.0 mg min-

1) had no signicant effect on the captopril

removal efciency. This result is probably because

the ozone dosage of 1.0 mg min-1 reached the

maximum ozone utilization of the ZnO/Fe2O3

nanocomposite. Thus, the optimum ozone dosage

was selected as 1.0 mg min-1 [21, 22]. He et al.

removed the metoprolol and ibuprofen using

catalytic ozonation; their results showed that in

optimal conditions, the catalyst dosage was 0.1 g

L-1 [21].

Bai et al. removed the sulfamethazine using a

catalytic ozonation process (Ce0.1Fe0.9OOH as a

catalyst), their results indicated that under optimal

conditions including pH of 7.0, catalyst dosage

of 0.2 g L-1, ozone dosage of 15 mg min-1, and

sulfamethazine concentration of 20 mg L-1, TOC

removal efciency was obtained of 44% at during

120 min [23]. In addition, Qi et al. removed the

phenacetin using catalytic ozonation with CuFe2O4

and its precursor; their results showed that in

optimal conditions (pH of 7.72, catalyst dosage

of 2.0 g L-1; ozone dosage of 0.36 mg min-1, and

phenacetin concentration of 0.2 mM), the TOC

removal efciency was obtained of 90% at during

180 min [24]. Moreover, Zhao et al. removed the

phenol using catalytic ozonation with NiFe2O4

as a catalyst; their results showed that in optimal

conditions (pH of 6.5, catalyst dosage of 1.0 g

L-1; ozone dosage of 0.75 mg min-1, and phenol

concentration of 300 mg L-1), the phenol removal

efciency was obtained of 38.9% at during 60 min

[25].

4. Conclusion

This current study aims to evaluate the removal

efciency of captopril using ZnO/Fe2O3

nanocomposite as a low-cost catalyst by a catalytic

ozonation process. The maximum captopril

removal efciency was 99.4% under optimal

conditions. During catalytic ozonation, catalysts

can promote the ozonation process and generate

active free radicals. It enhanced the degradation

and mineralization of organic contaminants.

Solution pH and initial captopril concentration had

an inverse effect, and the catalyst and ozone dosage

directly affected the removal efciency of captopril.

The catalytic ozonation process is an eco-friendly

advanced oxidation process successfully applied to

remove captopril from polluted water.

5. Acknowledgements

The authors would like to express their appreciation

to the student research committee of Kerman

University of Medical Sciences [Grant number

401000072] for supporting the current work.

Funding: This work received a grant from the

Kerman University of Medical Sciences [Grant

number 401000072].

Conict of interest: The authors declare that they

have no conict of interest regarding the publication

of the current paper.

Ethical approval: The Ethics Committee of

Kerman University of Medical Sciences approved

the study (IR.KMU.REC.1401.099).

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Anal. Methods Environ. Chem. J. 5 (3) (2022) 40-54

Research Article, Issue 3

Analytical Methods in Environmental Chemistry Journal

Journal home page: www.amecj.com/ir

AMECJ

An efcient cheap source of activated carbon as solid phases for

extraction and removal of Congo Red from aqueous solutions

Tahrer N. Majid a and Ali A. Abdulwahid a,*

aUniversity of Basra, College of Science, Chemistry Department, PO Box 49, Basra, Iraq,

ABSTRACT

The present study reported the preparation of solid phases from

various available and cheap natural sources represented by activated

carbon to remove the polluting dye Congo Red (CR). Activated

carbon derived from the leaves of the Consocarpus plant (C/AC)

and Ziziphus Spina-Christi plant (Z/AC) and Myrtus plant (M/AC)

by chemical activation. The prepared solid phases were diagnosed

and examined using FTIR, FESE, and XRD. The results of the study

indicated that the best amount for the solid phase was 0.25 g for the

three solid phases used against dye, the optimal concentration of the

CR was 100 mg L-1, and the optimum acidity function was equal to 5

with a volume of 25 mL, as the optimization experiments indicated

that the best ow rate of the eluting solution was equal to 0.5 ml

min-1. The elution processes were carried out using several solvents

different in polarity and it was found that 8 mL of DMSO achieved

the best percentage of recovery (%R). Also, this study included

calculating adsorption capacity based on the optimal conditions

that were obtained by applying Langmuir and Freundlich isotherm

models, and qmax, according to the Langmuir model, was (21.74,

23.53, 22.17) mg g-1 for (Z/AC), (C/AC), and (M/AC) adsorbents,

respectively.

Keywords:

Solid phase extraction,

Active carbon,

Congo Red,

Enrichment factor,

UV-Vis technology

ARTICLE INFO:

Received 17 May 2022

Revised form 28 Jul 2022

Accepted 19 Aug 2022

Available online 29 Sep 2022

*Corresponding Author: Ali A. Abdulwahid

Email: ali.abdulwahid@uobasrah.edu.iq

https://doi.org/10.24200/amecj.v5.i03.205

1. Introduction

In recent years, human pollution of natural waters has

led to a signicant reduction in operational freshwater

resources on Earth [1]. These pollutants from multiple

sources have caused signicant environmental and

health problems that threaten society and living

organisms [2, 3]. Many contaminants such as toxic

heavy metals, and organic contaminants, such as

dyes, pesticides, drugs, degraded organic matter,

and so on, are present in polluted waters [4]. Among

these pollutants are dyed [5]. A dye is a coloring

substance that can be natural, semi-synthetic,

or fully synthetic and blend with the substrate to

which it is applied. Natural dyes can be non-toxic

compared to synthetic dyes due to their natural

origin. The primary sources of pollution of synthetic

dyes are the textile, rubber, paper, plastic, printing,

paint, and leather industries [6]. It is estimated that

about 10,000 types of articial and natural dyes are

produced annually worldwide, with a signicant

number of dyes being wasted during manufacturing

and application processes [7]. The main reason is

the incomplete adhesion of the paints to the layers

when painting. The amount of unstable dyes in

textile efuents is higher than that of efuents

discharged by other industries [8]. Many chemicals

and dyes remain unused during the dyeing process

of textiles, releasing excess liquid dye into the

environment. It is estimated that textiles subject

------------------------

Extraction and Removal of Congo Red by Activated carbon Tahrer N. Majid et al

to dyeing can absorb about 80% of dye liquor due

to their limited adsorption capacity [9]. Of all the

colors, "azo" colors are most often used to dye

different substrates. They are complex in nature

and are potentially carcinogenic. Due to the larger

molecular structures, their decomposition products

are also toxic [10]. If azo dyes are absorbed into the

soil from the water, they can alter the chemical and

physical properties of the soil. This can lead to the

destruction of the vegetation in the environment; if

the toxic chemical dyes remain in the soil for a long

time, they also kill benecial microorganisms in

the soil, signicantly affecting agricultural fertility

[11]. Therefore, these toxic dyes should be disposed

of from wastewater as much as possible before they

are released into terrestrial or aquatic resources in

an environmentally sound manner [12]. The search

for efcient and safe technologies for removing

organic paints from aquatic systems is of great

interest for environmental protection. The best

water treatment methods chosen depend on several

factors, including the nature, quantity and quality

of the paint materials in the systems analyzed

[13]. Great attention has been paid to technologies

for removing paint from wastewater, and many

chemical, biological and physical methods have

been developed for this purpose [14,15], including

adsorption, chemical oxidation, photocatalysis,

electrochemical oxidation, biodegradation, ion-

exchange ltration, coagulation/occulation,

membrane ltration, catalytic degradation

and so on. Most conventional methods have

major drawbacks of low selectivity, high power

consumption, and low color degradation [16].

Many attempts have been made today to develop

new selective and sensitive techniques for the

purication of samples and separation of selected

materials, and solid phase extraction (SPE) is the

most widely used method [17], As SPE for sample

pretreatment offers several advantages, including

fast separation, low cost, low solvent consumption,

high enrichment efciency and recovery rates,

short processing times, no emulsion formation,

and the ability to combine with many advanced

detection methods [18], simple composition, high

recovery and high enrichment factor. The basic

principle of the elements/species of particular

interest is to transfer the target elements/species

from the sample matrix to the active site of the

SPE adsorbent. The sorbent is the main factor

that determines the selectivity, sensitivity, and

extraction/absorption dynamics of the relevant

method [19]. In this study, three natural materials

were selected to convert them into activated carbon

and use the products as a solid phase in the study of

the solid phase extraction technology (SPE), where

Ziziphus Spina-Christi leaves, Consocarpus leaves

and Myrtus Communis leaves were used. Materials

in the preparation of solid phases (Z/AC), (C/AC)

and (M/AC) respectively to remove Congo red

(CR) in aqueous solutions using SPE under optimal

conditions.

This paper aims to investigate the applicability of

activated carbon prepared from cheap and available

natural sources as a solid phase in SPE for the

purify water contaminated with organic Congo red

(CR) dye, [1-naphthalene sulfonic acid, 3, 30-(4,

40-biphenylenebis (azo)) bis (4-amino-) disodium

salt] (Fig. 1).

Fig. 1. Chemical structure of Congo red

2. Experimental

2.1. Chemicals and Materials

Chemical reagents including Congo Red (CR), 85%

dye content (C32H22N6Na2O6S2, Mw: 696.665 g mol-

1) purchased from (Pub Chem). A stock solution

(100 mg.L-1) of (CR) was prepared by dissolving the

required amount of dye in distilled water. The pH was

adjusted with 0.1 mol L-1 of NaOH (Univar) and 0.1

mol.L-1 HCl (AnalaR) and measured with a pH meter

(model SD 300, Germany). The potassium hydroxide

(KOH), (Sigma-Aldrich) was used to activate the

carbon that was prepared from multiple natural

sources (Ziziphus Spina-Christi leaves, Consocarpus

leaves, and Myrtus communis leave). The ethanol,

methanol, dimethyl sulfoxide (DMSO), n-Hexane,

and toluene (Sigma-Aldrich) were used in the solid

phase elution to recover the dye. Distilled water was

used throughout this study. AC was distinguished

by FT-IR, XRD, TEM and SEM technologies. The

absorbance of the CR dye solution was measured

at the wavelength of 494 nm, using a UV-visible

spectrophotometer (PG Instrument T80 + UV/VIS

model). The percentage of dye removal efciency, R

and the amount of CR dye adsorbed per unit weight

of adsorbent at time t, qt (mg g-1) was calculated as

Equation 1 and 2:

(Eq.1)

(Eq.2)

Where Ce is the concentration of CR at time t, C0 is

the initial dye concentration (mg L-1), M is the mass

of adsorbent (g) and V is the volume of solution (L).

2.2. Activated carbon preparation

Three categories of activated carbon were produced

from Ziziphus Spina Christi leaves, Consocarpus

leaves and Myrtus communis leaves, and were denoted

by (Z/AC), (C/AC) and (M/AC) respectively. The

leaves of the plants were collected and washed well

with distilled water; then each substance was boiled

in two liters of water for two hours, to remove other

water-soluble organic and phenolic compounds, then

dried at 70°C in Oven for 8 hours. Subsequently, they

were crushed and sieved (40–60 mesh). Afterward,

125 g of each type of dried plant leaf powder was

used as the initial amount to produce every kind of

activated carbon and impregnation of the plant leaves

in a potassium hydroxide KOH (25%) by using a

solution (KOH) to solid (plant leaves powder) ratio

of 3:1 for 24 h, and then rinsed with distilled water

several to reach the pH of the washing liquid. Then,

the washed solid samples were dried at 100 °C; then

pyrolyzed in a mufe furnace at 500 °C carbonization

temperature for 1 hour. After that, the samples were

washed with deionized water many times until the pH

of the solution was equal to the pH of the distilled

water. The resulting activated carbon was dried up

at 100 °C and kept dry till usage in the experiment

[20,21].

2.3. Solid phase extraction

The solid phase extraction method includes three

basic stages, column preparation, loading, and elution

[22,23]. The column of the polypropylene cartridge

was prepared (Fig. 2). The column was lled with a

permeable polypropylene lm (disc) with a thickness

of 1 mm. Four layers of glass paper were placed

glass lter paper; then the column was lled with a

xed weight (0.5 gm) of the solid phase, which is the

activated carbon prepared in this study from different

natural sources (Z/AC), (C/AC), (M/AC). The steel

was homogeneous, so, that it was free of voids and of

equal height from the top, then a layer of glass paper

was placed over the solid phase. The CR dye solution

was passed at the pHpzc, where the dye is bound at

this stage to the solid phase pre-packed in the column

and the unbound part of the dye passes from the

column as well as the rest of the original components

and at a running rate depends on gravity. As for the

rinsing stage, it included passing the elution solution

through the separation column, which breaks the

link between the dye and the solid phase, and then

transfers the solution to measurement using UV-

Anal. Methods Environ. Chem. J. 5 (3) (2022) 40-54

visible technology to know the concentration

extracted from the dye. The ratio can be calculated

as the percentage of recovery % through Equation 3,

and this study included nding the ideal conditions

for the optimization of the extraction process as

shown below.

(Eq.3)

2.4. Characterization Methods

To investigate the surface characteristic of (Z/

AC), (C/AC), and (M/AC), FT IR, XRD, and SEM

spectra were studied. FT-IR spectroscopy was

carried out to determine the type and nature of the

functional groups present in the activated carbon.

The presence of these functional groups increases

heterogeneity and, thereby the extraction. The

spectra of (Z/AC), (C/AC), and (M/AC) samples

are shown in Table 1. To explore the crystal lattice

structure of activated carbon, an X-ray diffraction

pattern was carried out; Figure 3 shows the XRD

conguration of the three AC types (Z/AC), (C/

AC) and (M/AC). In this pattern, several peaks

were found corresponding to their semi-crystalline

nature. XRD spectra of the tted conditioners

revealed a sharp diffraction peak of 29.5° for all

solutions that (Z/AC), (C/AC), and (M/AC) and this

is evidence for the possible presence of potassium

compounds with high crystallinity after activation

with KOH. The SEM is a tool for characterizing

the surface morphology and physical properties

of the adsorbent surface. It helps determine the

particle shape, appropriate size distribution of the

adsorbent and porosity. The surface morphology

of the (Z/AC), (C/AC) and (M/AC) adsorbents are

shown in Figure 4a-c.

Fig. 2. Summary of preparation of activated carbon and extraction procedure

Extraction and Removal of Congo Red by Activated carbon Tahrer N. Majid et al

Table 1. FT-IR analysis (Z/AC), (C/AC) and (M/AC

Z\ACC\ACM\AC

3438.463754.733422.06O-H

3374.82-3302.5≡CH

3225.36-3267.79CH=

2369.12-2360.44≡CH

2948.63-2900.41CH-

1445.391432.851435.74C-O

-1609.13-C=C

Fig. 3. XRD pattern of a: (Z/AC), b: (C/AC) and c: (M/AC)

Anal. Methods Environ. Chem. J. 5 (3) (2022) 40-54

Fig. 4a. SEM of Ziziphus spina-christi (Z/AC)

Fig. 4c. SEM image of Myrtus plant (M/AC)

Fig. 4b. SEM of Consocarpus plant (C/AC)

Extraction and Removal of Congo Red by Activated carbon Tahrer N. Majid et al

3. Results and Discussion

3.1. Optimization of the extraction procedure

The study of nding the optimal conditions for any

analytical method includes the process of changing

one of the conditions of the experiment and xing

the rest of the other conditions that control the

efciency of the experiment. Adjusting the method

to all the optimal values for all factors, and to

nd the ideal conditions and obtain the maximum

efciency of the process of extraction and removal

of the dye, several experiments were conducted as

follows:

3.2. Amount of solid phase

The effect of the weight of the packed solid phase

in the separating column was studied, and the

results proved that the percentage of retrieval varies

according to the amount of the solid phase. Figure 5

shows an apparent behavior in increasing the retrieval

percentage with increasing phase weight for the

weights range (0.05-5.0) g, where the recovery

percentage reaches the maximum value when using

the weight of 0.25 g. Then the recovery percentages

stabilize in the largest weights down to 0.5 g. This

behavior was for all solid phases when studying the

CR dye, which leads to the weight of 0.25 g of the

solid phase being selected as a constant weight for

all phases in all subsequent experiments.

Fig. 5. Effect of the solid phase amount on the recovery

of Congo Red

3.3. Effect of Dye concentration

The effect of the concentration of the CR solution

was studied after packing the extraction column

with 0.25 g of activated carbon and loading CR

with a range of concentrations which is (50-400)

mg L-1 with the stabilization of the acidity function,

the volume of the dye solution, the ow rate, the

type and volume of the rinse solution, where a

concentration of 100 mg L-1 was chosen for the CR

dye towards the corresponding solid phases, where

this concentration achieves a recovery percentage

ranging from 60-65% for the dyes. This ratio is

necessary because the recovery efciency was not

at this stage at its maximum, and it is expected to

increase it when conducting experiments on other

factors affecting extraction. Due to Figure 6, the

effect of the concentration of the CR solutions was

shown.

Fig. 6. Effect of Congo Red concentration on the

recovery percentage

3.4. Effect of pH

The pH function is one of the critical factors in

the study of extraction, which affects the surface

charge of the solid phase and the composition of

the dye [38]. The effect of acid functions on the

solid phase extraction process with a range of (2-

12) was studied. Figure 7 represents the effect of

the acidity function on the percentage of recovery

of CR (anionic) dye when extracted by (Z/AC) and

(C/AC) and (M/AC) phases, as we notice that the

%R values increase directly for the range of the

acidic function (2-5) and then reach the optimal

100

0100 200 300 400 500

Recovery , %

Conc. of CR , mg/L

(Z/AC)KOH

(M/AC)KOH

(C/AC)KOH

0 0.1 0.2 0.3 0.4 0.5 0.6

Recovery , %

Active Carbon Weghit , gm

(Z/AC)KOH

(M/AC)KOH

(C/AC)KOH

Anal. Methods Environ. Chem. J. 5 (3) (2022) 40-54

acidity function pH = 5 and this increase in the %R

values is attributed to the hydrostatic interactions

between the solid phases and dyes, as for the acid

functions that follow the optimum value and within

the range (6-12), we notice a decrease in the values

of %R, and this can be attributed to the fact that

the hydroxyl radical OH- whose concentration

increases with the increase of the acidic function

competes with the dye molecules towards the solid

phases. The value of the optimal pH function in

extracting or removing the CR dye is equal to 5

and was identical to the results of previous studies

[24,25].

Fig. 7. Effect of pH on the recovery of Congo Red

3.5. Effect of dyes volume

Studying the effect of the target material

solution’s volume is essential in determining the

optimal conditions for the solid phase extraction

method [26,27]. Figure 8 showed that the

percentages of recovery of CR dye were close to

100% for volumes less than 100 mL within the

range of volumes (100-400) mL, the percentages

of recovery gradually decreased. This behavior

was very logical because the efciency of the

extraction decreases with the increase in the

volume of the solution, as the concentration of

the dye decreases with the increase in the volume

of the solution, and therefore the remaining dye

during the extraction process is more diluted

the more the volume of the solution was more

signicant the extraction efciency decreased.

So, the volume of 25 mL is considered to be the

optimum volume of the CR dye.

Fig. 8. Effect of Congo Red solution volume on the

recovery percentage

3.6. Effect of ow rate

The effect of the ow rate of the dye solution is

one of the critical factors affecting the efciency of

extraction in the solid phase. A balance in the ow

rate is necessary in the sense that low ow rates

do not achieve high rates of recovery of the target

material due to the possibility of disengagement

between the solid phase and the target material

during the passage of the solution. Thus, the

extraction efciency decreases, and high ow rates

are considered undesirable because they do not

provide sufcient time for the connection between

the solid phase and the material to be extracted.

Figure 9 shows a graphic relationship between the

percentages of dye recovery versus the rate of the

ow rate of the CR solution. We found that the

maximum ow rate was equal to 0.5 mL min.

Fig.9. Effect of ow rate on the recovery of Congo Red

100

0246810 12 14

Recovery , %

(Z/AC)KOH

(M/AC)KOH

(C/AC)KOH

100

010 20 30 40 50 60

Recovery , %

Volume of CR , mL

(Z/AC)KOH

(M/AC)KOH

(C/AC)KOH

100

0 1 23 4 5 6

Recovery , %

Flow Rate , ml/min

(Z/AC)KOH

(M/AC)KOH

(C/AC)KOH

Extraction and Removal of Congo Red by Activated carbon Tahrer N. Majid et al

3.7. Effect of type and volume of eluting solution

Table 2 shows the solvents used as eluent solutions

and their polarity index values, where the polarity

coefcient represents the ability of the solvent

to interfere with the solute[28], and Figure 10

shows the effect of the type of the solvent on the

percentages of recovery of the two dyes. We note

that the highest rate of recovery was achieved when

the elution solution was DMSO with a polarity

coefcient of 7.2 and the highest polarity among

the solvents. It may be attributed to the great

afnity of CR dyes towards the DMSO solvent

because it is a polar dye. It makes the dye leave as a

solid phase and moves with the more polar rinsing

solution (Figure 10). we note that the percentages

of recovery decrease with the decreasing polarity

of the eluting solution. The study also included

nding the optimum volume of the rinse solution;

when observing in Figure 11, which represents the

graphic relationship between the percentage of

recovery of the CR dye and the volume of the rinse

solution, we nd that the volume that achieves the

highest rate of recovery was equal to 8 mL. Finding

the optimal volume of the rinsing solution leads us

to calculate the enrichment factor, which evaluates

the extraction process, which can be calculated

from Equation 4 [29].

(Eq.4)

The enrichment coefcient can be calculated

depending on the initial dye volume and the volume

of the rinsing solution (Equation 4). Table 3 shows

the values of the calculated enrichment coefcients

for the extraction systems under study.

Fig. 11. Effect of DMSO volume on the recovery

of Congo Red

(Z/AC)KOH

(M/AC)KOH

(C/AC)KOH

100

DMSO

Methanol

Ethanol

Toluene

n-Hexane

Recovery , %

Eluent Type

Fig. 10. Effect of elution type on the recovery of Congo Red

100

0 2 4 6 8 10 12 14 16 18 20

Recovery , %

DMSO Volume , mL

(Z/AC)KOH

(M/AC)KOH

(C/AC)KOH

Anal. Methods Environ. Chem. J. 5 (3) (2022) 40-54

3.8. Isotherm study

One of the most important benets of the SPE

extraction process is the removal of the target

substance from its origin in which it is located

[30]. Therefore, the results obtained in the

extraction experiments can be employed in favor

of the removal operations of CR from its aqueous

solution. The residual concentration of the solutions

of the CR dye was calculated and thus the weight

adsorption capacity q (mg g-1) was calculated based

on Equation 5 [31, 32].

(Eq.5)

Through the study of the isotherm, it is possible

to clarify the relationship between the solid

phases and dye, and to suggest the mechanisms of

interaction [33]. The study of the isotherm includes

the application of many models, and the Langmuir

and Freundlich models were chosen in this study.

3.9. Langmuir isotherm model

The Langmuir equation [34] which was developed

in 1916 applies to monolayer or single-molecular

adsorption of the target material on the surface

of the adsorbent material or the solid phase

(Equation 6), where this equation assumes the

existence of homogeneous adsorption sites [35].

(Eq.6)

Figure 12 represents the Langmuir model for CR.

Table 4 also shows the results obtained from this

model. The values of the maximum adsorption

capacity qmax, Langmuir constant KL and correlation

coefcient R2 were calculated by plotting the

graphical relationship of the Langmuir equation

between Ce/qe on the Y-axis and Ce on the X-axis

as in Figure 12, where the slope of the straight line

represents (1/qmax) and the cutoff represents (1/

qmax. KL) and by noting the Table 4, we nd that

the maximum adsorption capacity of CR dye by

the solid phase (C/AC) is the highest in comparison

with the other two phases. This may be due to the

nature of the interaction between this dye and the

prepared solid phases, which certainly had the

advantage compared to the nature of the association

with CR dye, and also through Table 4 we nd that

the values of Langmuir constant rise in the same

pattern, which indicates the extent of the strong

interaction between the active sites in the dye and

between the solid phase. It is also noted the values

of the correlation coefcient very close to the right

one, which indicates the relative applicability of

the studied adsorption systems on the Langmuir

model.

Table 2. Solvents used as elution solution and their polarity index

Polarity indexSolvent

7.2DMSO

5.1Methanol

4.3Ethanol

2.4Toluene

0.1n-hexane

Table 3. Enrichment factors for extraction of CR

Enrichment factorSolid Phase

3.125(Z/AC)

3.125(M/AC)

3.125(C/AC)

Extraction and Removal of Congo Red by Activated carbon Tahrer N. Majid et al

3.10. Freundlich isotherm model

As Equation 7, the Freundlich equation developed

in 1926 [36] It explains the processes of interference

and adsorption that occur on heterogeneous

surfaces and assumes that adsorption occurs at sites

of varying adsorption energy [37].

(Eq.7)

The Figure 13 represent Freundlich model for

CR. Table 5 also shows the results obtained from

this model. The values of Freundlich constant KF

and correlation coefcient R2 were calculated by

plotting the graph of Freundlich equation between

lnqe on the Y-axis and lnCe on the X-axis as in Figure

13, where the slope of the straight line represents

(1/n) and the cut off represents (lnKF). By noting

the Table 5, we nd that the highest value of KF,

which represents the adsorption energy between the

solid phase and the dye [38] is for the adsorption

system of the solid phase (C/AC) and this result is

in agreement with the qmax values calculated from

the Langmuir model. The values of 1/n give an

indication that the adsorption process is preferred or

unfavorable, as if the values of 1/n = 0, this means

that the adsorption is irreversible, but when it is

0<1/n<1, this indicates that the adsorption between

the solid phase and target material is a preferred

process, and adsorption may not be favorable when

1/n>1 [39]. When observing the values of 1/n from

Table 5, we nd that they are greater than zero and

less than one for all solid phases. Thus, could be

concluded that the adsorption systems in this study

are preferred. After reviewing Tables 4 and 5, we

nd that the R2 values of the Freundlich model

for all systems are higher than the corresponding

values in the Langmuir model leading to suggest a

physisorption mechanism.

4. Conclusion

In conclusion, the efcient removal of the dyes

CR from aqueous solutions was observed when

using the active carbon (Z/AC), (C/AC) and (M/

AC) as solid phases. The optimization approach

y = 0.046x + 0.2958

R² = 0.9938

y = 0.0451x + 0.2364

R² = 0.9933

y = 0.0425x + 0.1692

R² = 0.9905

0.5

1.5

2.5

3.5

4.5

0 20 40 60 80 100

Ce /q , (g/L)

Ce , (mg/L)

(Z/AC)KOH

(M/AC)KOH

(C/AC)KOH

Fig. 12. Langmuir isotherm of adsorption of Congo Red

Table 4. Langmuir isotherm parameters for the adsorption of CR dye at 25 °C

qmax(mg. g-1)Solid Phase

1.55510.993821.7391(Z/AC)

1.907780.993322.1729(M/AC)

2.511820.990523.5294(C/AC)

Anal. Methods Environ. Chem. J. 5 (3) (2022) 40-54

for the extraction of CR observed that the optimum

amount of solid phases was 0. 25 g, the initial

concentration of dye solution was 100 mg L-1, the

optimum pH was 5, the volume of dye solution was

25.0 mL with a ow rate equal to 0.5 mL min-1,

and the optimum elution solution was DMSO with

a volume equal to 2.0 mL, from the linearized form

(from the calculation of the Langmuir equation,

qmax), values for the CR dye were (21.74, 23.53,

22.17) mg g-1 for (Z/AC), (C/AC), and (M/AC),

respectively.

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Anal. Methods Environ. Chem. J. 5 (3) (2022) 40-54

Anal. Methods Environ. Chem. J. 5 (3) (2022) 55-69

Research Article, Issue 3

Analytical Methods in Environmental Chemistry Journal

Journal home page: www.amecj.com/ir

AMECJ

Optimization and effect of varying catalyst concentration

and trans-esterication temperature on the yield of biodiesel

production from palm kernel oil and groundnut oil

Obidike Blessing Magarette a, Okwara Nelson Onyekachib, Andrew Wirnkor Verlac,

Christian Ebere Enyohd,* and Mbagwu JohnPaule

aDepartment of Chemical Sciences, Akwa-Ibom State Polytechnic Ikot-Osurua, Ikot-Ekpene Nigeria.

bEunisell Globals Limited, Victoria Island, Lagos State Nigeria.

cDepartment of Chemistry, Imo State University Owerri, Nigeria.

d,* Graduate School of Science and Technology, Saitama University, Saitama, Japan

eDepartment of Physics and Astronomy, University of Kansas, USA

ABSTRACT

The negative environmental impact generated by fossil fuel has

resulted in the demand to search for alternative routes of renewable

sources of energy, such as biodiesel, that have unlimited duration while

having little or no hazardous impact. In this study, trans-esterication

of palm kernel oil and groundnut oil was carried out using sodium

methoxide (CH3ONa) as a catalyst. The effect of varying Sodium

Methoxide (CH3ONa) catalyst concentrations of (0.25, 0.5, 1.0, 1.5,

and 2.0) % w/v at trans-esterication temperatures of (50, 55, and

60) oC on the yield of biodiesel from groundnut oil and palm kernel

oil was determined. This was to identify the catalyst concentration

and trans-esterication temperature with optimal process yield. The

process gave optimum biodiesel yields of 98% and 84% by volume of

groundnut oil and palm kernel oil at reaction conditions of 0.5%w/v

CH3ONa as catalyst, trans-esterication temperature of 55oC, 360

rpm mixing rate and a reaction time of 90 minutes. The biodiesel

produced was analyzed for fuel properties using the American

Society of Testing and Materials (ASTM) standard, and the results

obtained were as follows; specic gravity (0.8835, 0.8815 at 15oC),

ash point (98, 124) oC, viscosity (5.2, 7.6) mm2S-1at 40oC, pour point

(9, -1)oC, iodine value (8.04, 17.11) /100, acid value (0.67, 0.48) mg/

KOH/g, peroxide value (28, 60) mg Kg-1, re point (108,136)oC for

palm kernel oil and groundnut oil respectively.

Keywords:

Biodiesel,

Trans-Esterication,

Mineral diesel,

Palm kernel oil,

Groundnut oil,

Optimization

ARTICLE INFO:

Received 8 May 2022

Revised form 16 Jul 2022

Accepted 11 Aug 2022

Available online 30 Sep 2022

*Corresponding Author: Christian Ebere Enyoh

Email: cenyoh@gmail.com

https://doi.org/10.24200/amecj.v5.i03.203

1. Introduction

Considering the rapid increase in the global

population in the world today, the long-term

strength of a complex environment is tested

by the demand for a higher standard of living.

This involves meeting the energy and food

requirements of over 9 billion people [1]. A

recent statement by BP’s Energy Outlook to 2035

proposed that the average world energy usage

is expected to increase by 34% between 2014

and 2035 [2]. However, the use of petroleum

is a suitable means of harnessing energy for

global consumption. But its drastic increase in

price, non-ecofriendly nature, and great addition

to pollution of the atmosphere have led to the

need to develop alternative routes of renewable

sources of energy that have unlimited duration

------------------------

while having little or no hazardous impact on

the environment [3]. Several alternative means,

such as bio-ethanol from the ebullition of starch,

biomass gasication, and biodiesel, have been

harnessed over the years [4]. However, the use of

biodiesel remains the best. It covers an estimated

82% of the total biofuel production as stated by the

EU. It has also shown a substantial contribution

to future energy demands of both domestic and

industrial sectors [5,6]. In comparison with

petroleum-based derived diesel, it is non-toxic,

biodegradable, and a cleaner source of energy

[2]. Vehicles using biodiesel emit less harmful

greenhouse gases of carbon monoxide and sulfur

dioxide [7]. Biodiesel could reduce the emission

of particulate matter (PM) and act as a good

lubricant for diesel engines, thus prolonging the

shelf-life of the engine. In addition, biodiesel has

a higher ash point, making it safer to handle than

mineral diesel [8]. Other protable characteristics

of biodiesel that make it an effective alternative

to mineral-derived-diesel oil are liquid nature

portability, sustainability, ignition performance,

and higher octane number [9]. Biodiesel, also

known as fatty acids methyl esters (FAME)

is a domestic and renewable biomass fuel for

diesel engines obtained from vegetable oils or

animal fats, designated B100. It must meet the

requirements of ASTM D6751 [8]. Feedstocks

used in biodiesel production are available and

could always be re-planted or grown [8]. Biodiesel

is produced through chemical processes such as

transesterication or esterication reactions [10].

Trans-esterication is the reaction between an

alcohol and an ester [11], while esterication is the

reaction between a carboxylic acid and alcohol.

During the process of trans-esterication, the

alcohol functional group is deprotonated by the

action of the base which compels it into a stronger

nucleophile [12]. The most frequently employed

alcohols in this process are ethanol or methanol.

Under standard conditions, the trans-esterication

reaction proceeds at a very slow rate or not at all,

so, heats and catalysts (acid and/or base) are used

to increase the reaction rate.

[13]. It is vital to know that catalysts are not

absorbed during trans-esterication reactions

[11]. Heterogeneous, homogeneous, Nano, and

super-critical uid catalysts have all been utilized

to activate trans-esterication reactions [14]. But

in this study, the homogenous catalyst is used for

the trans-esterication process. This is because

it permits a higher degree of interaction with

the reaction mixture, and allows the complete

conversion of feedstock to biodiesel [6]. More

often in the presence of a base catalyst, an

undesirable saponication reaction could occur if

the feedstock contains free fatty acids. Therefore,

feedstock containing less than 0.5wt% free fatty

acid is employed during the trans-esterication

process to avoid soap formation [15]. The

feedstock composition controls the chemical

pathway and dictates the type of catalyst to be

utilized in the production of biodiesel [2]. The

feedstock used for biodiesel production is Fats

and oils from plants and animals; they comprise

triglycerides which are esters that contain three

fatty acids, trihydric alcohol, and glycerol. The

feedstock includes a range of edible vegetable

oil, non-edible oils, waste or recycled oils, and

animal fats [7, 9 -10]. Edible oils are connected to

edible biomass, examples are; soybean, rapeseed,

sunower, palm, coconut and linseed while the

non-edible biofuels are biomass fuel, ranging

from lignocellulose feedstock to municipal solid

wastes [16]. From literature reviews various

types of oil have been used, but in this study

the use of edible oils like unrened groundnut

nut oil and palm kernel oil is selected owing to

their unique properties. Groundnut oil is mild-

tasting vegetable oil with a high smoke point

compared to several cooking oils [17]. The oil

is obtainable in puried, unrened, cold pressed,

and roasted variations have a strong peanut avor

and aroma [15]. Palm kernel oil is edible plant

oil derived from the kernel of the oil palm [12].

Palm kernel oil is among one of the essential

oils that contain saturated vegetable fats, this is

because it is composed of 16-carbon saturated

fatty acid and excessive palmitic acid [13]. Palm

Anal. Methods Environ. Chem. J. 5 (3) (2022) 55-69

kernel oil is semi-solid at room temperature, stable

at high cooking temperatures and has extended

storage capacity [18]. Several studies have

conducted experiments on biodiesel production

using different catalyst types and feedstock to

varying temperatures as summarized in Table 1. In

this study, biodiesel will be produced from palm

kernel oil and groundnut oil through different

trans-esterication temperatures by varying

catalyst concentrations of sodium methoxide.

The result from this study will be a basis for

determining the optimal reaction conditions for

the production of biodiesel production.

2. Experimental

The data generated from the experimental results

were modelled using linear, interaction, pure

quadratic, quadratic, 3rd order polynomial, and 4th

order polynomial. From the result obtained, the

4th-order polynomial showed a good correlation

with the experimental results; demonstrating that

the model was useful for optimization. Newton

Raphson’s multivariable optimization technique

and Response Surface Methodology (RSM) were

further used to enhance the process parameters of

the trans-esterication reaction. Newton Raphson’s

multivariable optimization technique gave an

optimal yield of 100.5 mL and 90.7 mL for groundnut

oil and PKO FAME with a corresponding catalyst

concentration and trans-esterication temperatures

of (0.25%, 0.48%) and (51.3 oC, 50 oC). Whereas

the surface plots gave optimal yields of 104.8

mL and 89.8 mL with the catalyst concentration

and trans-esterication temperatures of (0.6%,

0.425%) and (58oC, 50oC) for groundnut oil and

Palm kernel Oil (PKO) based Fatty Acid Methyl

Esters (FAME). The ndings from this study were

in good correlation with ASTM standards for fuel.

Therefore, it can be used as an excellent alternative

fuel for diesel engines.

2.1. Materials

The reagents used were distilled H2O, Concentrated

Sulphuric acid (H2SO4), Methanol (CH3OH),

Sodium hydroxide (NaOH), and two different oils,

namely groundnut and palm kernel. Reagent like

NaOH was properly reserved in an airtight plastic

container to prevent them from absorbing moisture

from the atmosphere since it is deliquescent in

nature. Methanol was reserved in an airtight brown

bottle to prevent evaporation as methanol is a

volatile liquid.

Table 1. Literatures reviews of some studies conducted on the effect of varying catalyst concentration

and Trans-esterication temperature on the yield of biodiesel in Nigeria

N Feed Stock Catalyst Type T Catalyst Concentration RT Biodiesel Yield Ref.

1. Palm kernel

oil Homogeneous 60oC,1.5 ,1.25 ,1.0 ,0.75 ,0.5)

and 2.0)%w/v of KOH 1.75 120 ,85.2 ,95.8 ,95.0 ,90.5)

%(71.3 ,71.1 ,73.3 [19]

2. Milk Bush

seed oil

Heterogeneous

Homogeneous 65oC wt. % of CSS and KOH 3.0 120 and 94.33% 81% [20]

3. False Shea

seed oil Homogeneous 50oC 0.3mol/dm3 of NaOH 120 85.0% [21]

4. Water Melon

Seed oil Homogeneous 60oC g of NaOH(018 ,015 ,0.13) (150 ,120 ,90) %(49 ,53 ,70) [22]

5. Jatropha

curcas oil Homogeneous 48oC 0.88M of KOH 240 84.70% [23]

6. Palm kernel

oil Homogeneous 60oC w/v of KOH 1.0% ,90 ,75 ,60 ,45 ,30)

(120 ,105

,94.2 ,92.5 ,90.1 ,87.4)

%(96.0 ,96.0 ,96.0 [24]

7. PKO-GO Homogeneous 55oC w/v of NaOH 0.7% -------------- 91.98 ,90.53 [25]

RT: Reaction time (mins) T:Temperature PKO-GO: Palm kernel oil and groundnut oil

Effect of Catalyst and Transesterication on the Biodiesel Production Obidike Blessing Magarette et al

2.2. Sampling

Groundnut oil and Palm kernel oil were procured

from a commercial shop in Ogbete main market

Enugu state, Nigeria. The experiment was

conducted in laboratory 3 of the materials and

Energy Technology (MET) department of the

Project Development Institute (PRODA), Enugu

state Nigeria.

2.3. Acid-catalyzed esterication

Delving directly into base-catalyzed trans-

esterication may result in soap production

instead of biodiesel due to the high FFA content

of the unrened groundnut oil and palm kernel

oil. in order to eradicate the possibility of this side

reaction (i.e., saponication), the FFA content of the

unrened sample is reduced to the barest minimum

by acid-catalyzed esterication reaction using conc.

Sulfuric acid (conc.H2SO4) as catalyst [8]. The

diagrammatic setup is shown in Figure 1a and 1b.

2.3.1.Experimental procedure of the acid-

catalyzed esterication

Unrened groundnut oil and palm kernel oil

were poured into a conical ask and heated

to a temperature of 60oC for 10 minutes. The

temperature was monitored using mercury in a

glass thermometer tted with a ca lamp in the retort

stand. Methanol (60% weight of the sample) was

introduced into the beakers containing the preheated

oil samples. Concentrated sulfuric acid (H2SO4) of

1.2% weight of the sample was added to the mixture.

The mixture was stirred using a magnetic hot plate

at 50o C in an open system for an hour. The mixture

was transferred into a separating funnel and allowed

to separate overnight. The mixture is divided into

three phases: the lower phases (impurities), the

middle phase ( the preheated sample) and the upper

layer (the methanol-water phase).

2.4. Base catalyzed transesterication

experimental procedure

9.65g of NaOH pellets were weighed and

introduced into a round bottom ask containing

200mL of CH3OH(aq). It was stirred and allowed

to dissolve completely by shaking vigorously until

a solution of sodium-methoxide (CH3ONa) was

formed in the process. The CH3ONa solution was

added to 100mL of groundnut oil and palm kernel

oil from the acid catalyzed esterication process

into the different conical asks. The mixture was

then heated to a preferred trans-esterication

temperature of 60o C using the magnetic hot plate.

At this point, the stirrer was introduced into the

solution. Stirring was done at a constant speed

(e.g., 360 revolutions per minute). It was continued

until a given time of 90 minutes was attained.

While heating and stirring simultaneously, the

solution was made air-tight using a masking

foil to prevent CH3ONa from evaporating. After

Anal. Methods Environ. Chem. J. 5 (3) (2022) 55-69

Fig. 1a. Low FFA oil after acid-catalyzed esterication Fig. 1b. High FFA oil before acid catalyzed esterication

the given time, the solution was removed from

heat and poured into a separating funnel. It was

left overnight for the separation to take place.

Glycerin settled below, while the biodiesel (ethyl

esters) which was the supernatant settled above.

The glycerin was discarded and the biodiesel was

washed with distilled water until the impurities

were completely removed. These impurities were

in the form of a foamy solution that settled. The

biodiesel was again washed with hot water to

remove further impurities. Measurements were

also taken before and after the washing of biodiesel.

The waste product removed with water was tested

using phenolphthalein, which turned pink on

the addition of phenolphthalein, conrming that

sodium hydroxide was still present. So, in other

to get purer biodiesel, continued washing with

water was done until the product was removed as

waste does not turn pink using the phenolphthalein

Indicator. To neutralize the presence of NaOH(aq)

ultimately, 1mL H2SO4(aq) was added after every

negative phenolphthalein test because acids have

no negative effect on biodiesel. The already

washed biodiesel was collected and heated

gradually at about 100 to give off the leftover

water after washing, then was allowed to cool. A

viscous solution with pale gold color was obtained

and that was the biodiesel. The procedure was

repeated using the same catalyst concentrations of

0.25%w/v at the trans-esterication temperature

of 55oC and 50oC, respectively.

2.5. Physiochemical Characterization of

Biodiesel

2.5.1.Determination of specic gravity at 55oC

and viscosity at 40oC

empty S.G. bottle was weighed and lled with

distilled water, and the reading was noted. An S.G

bottle was lled with biodiesel and weighed again.

The S.G. was calculated using Equation 1.

(Eq.1)

The viscosity of the biodiesel was determined

using “Ostwald’s Viscometer”. This was done by

lling the viscometer to the mark; sucking it up into

the other side of the fuse, and setting a stop-clock

or stop-watch to time when the oil ows back to

the rst tube with which the oil was rst lled. The

viscosity was then calculated as Equation 2.

(Eq.2)

Where; 4.39 = centistokes constant, 8 = sugar or

glucose constant, t = time taken to move in the

viscometer.

2.5.2.Free fatty acid (FFA) or acid value

The acid number test was conducted using

ASTM D-664 Test Method. 5g of the biodiesel

sample was measured into a conical flask, and

three drops of phenolphthalein indicator and 20

ml of ethanol were added. It was titrated with

0.1 M NaOH solutions and a pink coloration

was observed. The FFA was calculated by

Equation 3.

(Eq.3)

Where; T.V = Titre value, N = Normality of titrate,

5.61 = Acid constant, W = Weight of the sample

2.5.3.Saponication Value (SV)

The saponication value test for biodiesel in

this present study was conducted in accordance

to ASTM D5558 standard testing method. 5g of

the biodiesel was measured into a conical ask,

0.5M of ethanolic KOH was added and reuxed

(heat) in a round bottom ask, then allowed to

stand for 3 minutes. The essence of reuxing

was to get a perfect dissolution of biodiesel in

the ethanolic potassium hydroxide. Three drops

of phenolphthalein indicator were added and

titrated with 0.5M hydrochloric acid. A blank

Effect of Catalyst and Transesterication on the Biodiesel Production Obidike Blessing Magarette et al

titration was also run; the saponication value

was calculated using Equation 4.

(Eq.4)

Where; V2 = Titer of blank, V1 = Titer of sample,

56.1 = MW of KOH, 0.5 = Normality of KOH.

2.5.4.Determination of iodine value using EN

14112 test method

5.0 g of biodiesel was measured into a conical

ask; 15mL of chloroform and 25mL of Wijis

(iodine monochloride) solution were added and

mixed together. The mixture was tightly covered

and placed in the dark for 30 minutes. 20mL of

10% KI (Potassium iodide) and 50mL of distilled

water were added and the resulting solution

turned to red. The reddish solution was titrated

with 0.1M Sodium Thiosulphate, 5.0 mL of 1%

starch indicator was added and the color turned

blue-black. It was later titrated with 0.1M Sodium

Thiosulphate and turned colorless. Blank was

also titrated and the iodine value was calculated

by Equation 5.

(Eq.5)

Where; 12.69 = Constant for iodine value,

N = Normality of Titrant, V2 = Titer of blank,

V1 = Titer of sample.

2.5.5.Determination of peroxide value using

ASTM D37031-13 methodology

5g of biodiesel was measured into a 100 mL

beaker, 25 mL of acetic acid and chloroform

solution in the ratio of 2:1 was added. 1mL of

10% Potassium Iodide was later added and shaken

vigorously. The mixture was covered and kept in

the dark place for 1 minute. 35 mL of the starch

indicator was added and Titrated with 0.02M

Sodium Thiosulphate Na2S2O3 and a white color

was observed. A blank titration was also prepared

in the same way as described excluding the step

of addition of biodiesel. The peroxide value was

calculated as Equation 6.

(Eq.6)

Where; N = Normality Na2S2O3, V1 = Titer of

sample, V2 = Titer of blank, 100 = Peroxide value

constant.

2.5.6.Determination of pour and ash point

This is the minimum temperature at which the oil

can to pour down. This test was done in accordance

to the ASTM D97 Test method. The biodiesel was

brought out at room temperature, it was allowed

to melt gradually and the temperature at which the

biodiesel became a complete liquid was recorded

as the pour point.

The ash point of an oil is the lowest temperature

at which vapour from biodiesel will ignite when a

small ame is applied under standard test conditions.

The test was carried out using the D93 test method.

A source of the re was placed at a distance away

from the smoking biodiesel in a closed cup and the

temperature at which the biodiesel catches re was

noted.

2.6. Model methodology

The yields of biodiesel obtained from both

samples (i.e., groundnut oil and palm kernel

oil) in this study were modeled concerning two

independent variables (catalyst concentration and

trans-esterication temperature) using Several

models such as linear, interaction, pure quadratic,

quadratic, 3rd order polynomial and 4th order

polynomials.

2.7. Optimization methodology

Data obtained were optimized using MATLAB

optimization tool box and Response Surface

Methodology (RSM) as described by [40].

Anal. Methods Environ. Chem. J. 5 (3) (2022) 55-69

3. Results and discussion

3.1. Experimental result on the yield of biodiesel

obtained from groundnut oil and palm kernel

oil by varying catalyst concentration and trans-

esterication temperature

The results obtained by varying transesterication

temperature from 50 - 60oC at catalysts concentration

of 0.25-2.0% w/v of CH3ONa is presented in Table

2 and 3. From the result it can be deduce that

biodiesel yield increases gradually with an increase

in catalysts concentrations and trans-esterication

temperature, but with an additional increase in

catalyst concentration of 1%w/v resulted to a

decrease in biodiesel yield. Hence, the maximum

output of biodiesel was at 0.5 % w/v of CH3ONa

catalyst and a trans-esterication temperature of

55oC. This implies that, at that temperature and

concentrations equilibrium is attained and this can be

further explained by trans-esterication reversible

reaction. The discovery from this research was in

close proximity to the works of [26] who reported

that catalysts concentrations above 1% w/v favored

backward reaction, thereby shifting the equilibrium

to the left as well as resulting in the loss of sodium

methoxide and a reduction in the yield of biodiesel.

3.2. Physicochemical characterization of the

biodiesel

The result for the physicochemical characterization

of the biodiesel is presented in Table 4. The

physiochemical characterization of biodiesel

obtained from PKO and groundnut oil in this

present study showed a good conformity to that

of ASTM standard values for mineral diesel.

Hence, it can be utilized as a better alternative

for petroleum diesel. The density of the oil is a

very vital factor to be considered because the fuel

injection system works with volume metering

approach. The density of biodiesel provides

required details on the weight of the oil at specic

temperatures. From this present study the specic

gravities of biodiesel harnessed from palm kernel

oil and groundnut oil were 0.8835 and 0.8815

respectively. These values are within the limits of

0.8833 of biodiesel specied by ASTM [27] and

were also in close proximity with various scientic

studies carried out by [28] who reported specic

gravities of 0.881, 0.865, and 0.887 for biodiesel

from Mango seed oil, Palm kernel oil and Shea

butter oil. Viscosity is one of the basic criteria

to be considered when evaluating the quality of

biodiesel. It is a key property which measures

the resistance ow of uids under the effect of

gravity [29]. The viscosity value obtained from

biodiesel of PKO and groundnut oil conducted in

this experiment are 5.2 mm2 S-1 and 7.6 mm2 S-1

respectively. These values were within the limits

of 4.0 - 6.0 mm2 S-1 specied by ASTM, but the

biodiesel from groundnut oil was a bit higher than

ASTM required limit. The viscosity of biodiesel

explains the effective lubricity of fuel; it shows

that the biodiesel analyzed in this present study

may protect diesel fuel pumps and engines from

wear and seepage. Thus enhances the atomicity

and combustion as well as reducing emissions of

fumes from exhaust engines. The values obtained

also showed good correlation with biodiesel

values of 7.65 and 5.92 mm2 S-1 from palm

kernel oil and groundnut oil [30]. It was said to

be somewhat higher than the values of 3.62 mm2

S-1 reported in shear butter oil [28] and mango

seed oil (5.82 mm2/S) [26]. Flash point refers

to the lowest temperature at which the biodiesel

produces enough vapour to ignite when exposed

to thermal sources; it is also a measure of degree

of ammability [31]. It is a basic criterion to

consider when handling, storing and transporting

fuel. The ash point of the biodiesel obtained from

PKO and groundnut oil in this research was 98oC

and 124oC. It was within the range of (100 – 170)

oC set by ASTM. Therefore, the ash point value

of the biodiesel from this research shows that it

is safe, non-hazardous, and can hardly ignite at

higher temperatures. The values obtained from

this research for biodiesel from PKO was slightly

lower than ash points of 120oC, 132oC, and 167oC

reported by [32-33]. The biodiesel from this study

is less volatile and free from basic impurities like

methanol which could reduce the ash point of

biodiesel.

Effect of Catalyst and Transesterication on the Biodiesel Production Obidike Blessing Magarette et al

The re point is the temperature at which the

biodiesel may like burn for a few seconds after

ignition in an open ame. The re point of

biodiesel of PKO and Groundnut oil obtained in

this experiment are 108oC and 136oC, it is higher

than ASTM values of 68oC for diesel [32]. This

shows that biodiesel is very suitable for use as it

can hardly burn even at higher temperatures after

ignition. The pour point is a necessary criterion

when evaluating the low-temperature Performance

of fuel. It is considered as the operational capacity

of the fuel under given weather, it shows how

effective biodiesels can be utilized even in cold

climatic regions. The ASTM specied value for the

pour point of biodiesel is -5 to 10 and -35 to 15 for

mineral diesel [27]. In this research the biodiesel

pours point values obtained from palm kernel oil

and groundnut oil were 9 and -1, respectively. These

values are within the ASTM standard values and are

in close range of 0.0oC, 2oC, 5oC, and 2oC pour point

values [32-34]. The biodiesel produced from the

palm kernel oil in this experiment has a high pour

point value of 9 due to the degree of unsaturation of

carbon to carbon (C-C) bond formed; this implies

that it can improve the performance of an engine.

Saponication value of biodiesel plays a vital role

in assessing adulteration [35]. Saponication of

biodiesel can be dened as the mass in milligram

of potassium hydroxide needed to saponify 1g of

oil, and it is relatively dependent on the average

molecular weight of fatty acids present in the

primary oil [28]. Saponication value is a measure

of degree on how the biodiesel oxidizes during

storage, an increase in saponication value increase

volatility of biodiesel. The saponication values of

biodiesel produced from PKO and groundnut oil

in this experimental study are 423.55 and 227.66

mg KOH g-1 respectively. It is above the ASTM

value of 120 mg KOH g-1. The high saponication

value is an indication that the primary oil had high

amount of soap content, this might result to uneven

combustion and increase emissions of thick fumes

from exhaust engine. However, it also has an the

advantage of purifying the internal component of

the engine, and as such reduces friction between

the surface parts of the engine [32]. Considering the

yield of biodiesel, high saponication values should

be reduced to the barest minimum as it would likely

prevent the separation of biodiesel from glycerin.

In comparison with other ndings, the values in

this study were obtained within the same range of

saponication values of 229.9 mg KOH g-1and 226

mg KOH g-1 obtained in biodiesel produced from

oil and palm kernel oil reported by [32,34].

Table 2. Palm Kernel Oil base FAME experimental results

Catalyst Concentration (Yield %)

Trans-esterication

Temperature (oC)

0.25 0.5 1.0 1.5 2.0

50 76 82 54 0 0

55 50 84 68 62 40

60 66 66 52 62 48

Table 3. Groundnut Oil base FAME experimental results

Catalyst Concentration (Yield %)

Trans-esterication

temperature (oC)

0.25 0.5 1.0 1.5 2.0

50 96 92 74 74 16

55 95 98 89 72 22

60 50 95 89 38 0

Anal. Methods Environ. Chem. J. 5 (3) (2022) 55-69

The acid content plays an important role when

evaluating the quality of biodiesel. It determines

how stable the biodiesel can stay over a long period

of time. The acid value is dened by the amount of

KOH in mg needed to neutralize 1.0 g of free fatty

acids [36]. The acid value of biodiesel produced

from palm kernel oil and groundnut oil in this

present study are 0.673 and 0.48 mg KOH g-1 which

was in good correlation with ASTM D 664 value of

0.5 mg KOH g-1. The acid values of biodiesel from

this experiment was also in a close range with values

of 0.37 mg KOH g-1, 1.2 mg KOH g-1, and 0.8 mg

KOH g-1 of biodiesel produced from Shea butter,

mango seed oil, and palm kernel oil respectively

[26,28,32]. The values obtained in this study shows

that the biodiesel is not corrosive. Iodine value

is a measure of degree of unsaturation resulting

from the formation of carbon to carbon bonds. It is

dened as the mass of iodine that is added to 100.0

g of oil [28]. Low iodine value signies presence

of saturation and vice versa, saturated oil has

resistance against oxidation and deterioration. The

iodine value for every biodiesel set by EN 14112 is

(7.5-8.6) g per100. In this present study, the iodine

value obtained from the biodiesel produced from

palm kernel oil and groundnut oil were 8.04 and

17.11. The palm kernel oil biodiesel was within

the specied range but that of the groundnut oil

was slightly above the range. This shows that

PKO biodiesel is a suitable alternative fuel for

diesel engines based specically on the measure

of iodine value. The PKO biodiesel possess low

oxidative resistance unlike that of groundnut oil,

although iodine value of biodiesel from groundnut

oil is technically on a good range when compared

with results of 65.09 g per 100, 34.24 g per100,

36.00g per100 of biodiesel from PKO, Shea

butter oil, and palm oil [32,28,33]. Peroxide value

plays a vital role on stability of biodiesel during

storage. It is dened by the amount of peroxide

oxygen per 1.0 kg of biodiesel. Peroxide value is

directly proportional to the rate of oxidation which

is greatly inuenced by the level of saturation of

the biodiesel. In other words, biodiesel with high

peroxide value will easily oxidize, thus increasing

the rate of biodegradation as well reducing its

stability [37]. The rate at which biodiesel undergo

oxidation is controlled by certain factors like

heat, amount of Oxygen, light, water content,

and temperature. Excessive heat, light and high

temperature enhances the rate of oxidation. In this

present study 28.0 meq kg-1 and 60.0 meq kg-1 was

recorded for biodiesel produced from palm kernel

oil and groundnut oil, this shows that biodiesel

produced from groundnut oil will easily degrade

compare to that from PKO.

Table 4. Properties of biodiesel and mineral diesel compared to biodiesel produced from Palm kernel oil

and Groundnut oil in this study.

Fuel properties Mineral-diesel ASTM

D975 Limits

Biodiesel ASTM

D6751 Palm kernel

oil biodiesel

Groundnut oil

biodiesel

Kinematic viscosity (mm2S-1)

at 40oC1.3 - 4.1 4.0-6.0 5.2 7.6

Specic gravity at 15oC. 0.85 0.88 0.8835 0.8815

Flash point (oC) 60-80 100 – 170

(ASTM D93) 98 124

Pour point (oC) -35 to -15 -5 to -10 (ASTM D97) 9 -1

Acid value (mKOH/g) - 0.5 ( ASTM D-664) 0.673 0.48

Peroxide value (meq/kg) - -ASTM D37031-13 28 60

Iodine value (g/100) - 7.5-8.6 (EN 14112) 8.04 17.11

Saponication

value (mgKOH/g) -95 – 370

(ASTM D5558) 423.5 227.66

Fire point (oC) - 68 108 136

Source: Biodiesel Handling and Use Guide (Fifth Edition). November 2016 for the standard properties for biodiesel and diesel fuels.

Effect of Catalyst and Transesterication on the Biodiesel Production Obidike Blessing Magarette et al

3.3. Modeling of Data generated from Trans-

esterication experimental result

Several models were used to t the experimental

data from the groundnut oil and PKO biodiesel. They

are linear, interaction, pure quadratic, quadratic, 3rd

order polynomial and 4th order polynomials with

their respective regression coefcients of 0.6694,

0.6695, 0.8981, 0.8982, 0.9213, and 0.9926 for

groundnut oil, while PKO was 0.4914, 0.7162,

0.5042, 0.7712, 0.8666, and 0.9773 as shown in

(Table 5). The F test was carried out by comparing

the variances of each model with the experimental

results, it shows that each of the models is actually

adequate because their calculated F values are less

than the F critical based on 14 degrees of freedom

for both the numerator and denominator. However,

regression coefcient of a model should be more

than or approximately equal to 0.95 [38-39].

Hence, the 4th order polynomial is obviously the

most suitable for both oils. The equation of the 4th

order polynomial for groundnut oil is at Equation 7.

Using the 4th order polynomial for both groundnut

and PKO, were generated at a constant temperature

(Figure 2(a) to Figure 2 (d))

(Eq.7)

Table 5. Data generated for different models used

0 X1 X2 Yexpt Ymodel (1) Ymodel (2) Ymodel (3) Ymodel (4) Ymodel (5) Ymodel (6)

Groundnut oil

10.25 50 96 106.3 106.9 102.2 87.43 92.51 98.79

20.25 55 95 98.3 98.3 94.4 91.65 90.49 91.22

30.25 60 50 90.3 89.7 85.9 70.26 62.91 50.98

40.5 50 92 96.4 96.8 98.7 94.15 94.91 87.37

50.5 55 98 88.4 88.4 90.9 98.54 99.95 103.3

60.5 60 95 80.4 80.0 82.3 77.34 79.41 94.35

71.0 50 74 76.6 76.7 84.4 90.58 83.92 75.63

81.0 55 89 68.6 68.6 76.6 95.34 96.11 89.70

91.0 60 89 60.6 60.6 68.1 74.51 82.71 86.66

10 1.5 50 74 56.9 56.5 60.7 64.36 57.64 74.81

11 1.5 55 72 48.9 48.9 52.9 69.48 67.73 67.99

12 1.5 60 38 40.9 41.2 44.4 49.02 52.19 41.19

13 2.0 50 16 37.1 36.4 27.6 15.48 23.02 15.38

14 2.0 55 22 29.1 29.1 19.7 20.98 21.73 23.81

15 2.0 60 0 21.1 21.8 11.2 0.874 -5.21 -1.19

R20.6694 0.6695 0.8981 0.8982 0.9213 0.9926

F1.4939 1.4939 1.2561 1.1133 1.0854 1.0075

F CRITICAL = 2.4837

Anal. Methods Environ. Chem. J. 5 (3) (2022) 55-69

Fig. 2. (a) Varying catalyst concentration at constant temperature for PKO base FAME and comparison

of the different groundnut oil base FAME models with the experimental data at (b) 50oC (c) 55oC (d) 60oC

PKO

10.25 50 76 65.38 83.02 61.91 76.30 77.40 72.593

20.25 55 50 73.58 73.58 69.59 77.06 62.36 53.121

30.25 60 66 81.78 64.14 77.99 57.42 57.89 66.286

40.5 50 82 59.26 71.39 59.86 68.33 77.25 89.138

50.5 55 84 67.46 67.46 67.54 74.61 72.91 77.801

60.5 60 66 75.66 63.53 75.94 60.48 69.46 65.061

71.0 50 54 47.02 48.13 51.68 48.69 51.58 47.491

81.0 55 68 55.22 55.22 59.35 65.99 68.28 72.941

91.0 60 52 63.42 62.32 67.76 62.88 66.52 53.368

10 1.5 50 0 34.79 24.87 38.03 24.10 14.18 3.5282

11 1.5 55 62 42.99 42.99 45.71 52.43 51.47 59.789

12 1.5 60 62 51.99 61.11 54.11 60.35 50.92 60.682

13 2.0 50 0 22.55 1.61 18.93 -5.43 -8.41 -0.7502

14 2.0 55 40 30.75 30.75 26.60 33.92 48.99 40.347

15 2.0 60 48 38.95 59.89 35.01 52.87 49.19 48.407

R20.4914 0.7162 0.5042 0.7712 0.8666 0.9773

F2.0352 1.3962 1.9834 1.2966 1.1539 1.0232

F CRITICAL = 2.4837

(1)=linear i.e. a_0+a_1 x_1+a_2 x_2

(2)=interaction i.e. a_0+a_1 x_1+a_2 x_2+a_3 x_1 x_2

(3)=pure quadratic i.e. a_0+a_1 x_1^2+a_2 x_2^2

(4)=quadratic i.e.a_0+a_1 x_1+a_2 x_2+a_3 x_1^2+a_4 x_1 x_2+a_5 x_2^2

(5)=3rd order polynomial i.e.a_0+a_1 x_1+a_2 x_2+a_3 x_1^2+a_4 x_1 x_2+a_5 x_2^2+ a_6 x_1^3+ a_7 x_1^2 x_2 a_9 x_2^3

(6)= 4th order polynomial i.e.a_0+...

X1=catalyst concentration as a percentage of weight of sample

X2=transesterication temperature(oC)

Y_EXPT=Yield from experiment (ml)

Effect of Catalyst and Transesterication on the Biodiesel Production Obidike Blessing Magarette et al

(a) (b)

(d)(c)

3.4. Optimization of parameters

The main aim of optimization is to obtain the process

parameter which gives the maximum FAME yield.

This was done using different techniques namely:

MATLAB optimization toolbox and response

surface methodology (RSM)

3.4.1.MATLAB optimization toolbox

This optimization toolbox uses the principle of

NEWTON RAPHSON’s method of multivariable

optimization technique. Firstly, a function was

created in a function M-le as given below for

groundnut oil and PKO base FAMEs respectively.

Function f = projopt1(x)

f=-(-1702+35.48*x(1)+79.3*x(2)+1292*x(1).^2-

47.97*x(1).*x(2)-0.8628*x(2).^2-581.6*x(1).^3

7.308*x(1).^2.*x(2)+0.9442*x(1).*x(2).^2-

49.42*x(1).^4+14.72*x(1).^3.*x(2)0.4235*x(1).^

2.*x(2).^2);

Function f = pkoopt(x)

f=-(4261-9215*x(1)-160.1*x(2)+1465*x(1).^2+37

8.5*x(1).*x(2)+1.498*x(2).^2+874.3*x(1).^3-

108.5*x(1).^2.*x(2)-3.709*x(1).*x(2).^2-

56.99*x(1).^4-10.67*x(1).^3.*x(2)+1.315*x(1).^2

.*x(2).^2);

Notice however that negative of the function

was minimized, as this gives the negative of the

maximum value of the function. Next, a program

was written to minimize the functions respectively

using the “fmincon” command as below table.

x0 = [0.25 50]; A = [1 1]; B = 62; lb = [0.25

50]; ub = [2 60];

[x fval] = fmincon (@projopt1, x0, A, B,

,lb,ub)

x0 = [2 60]; A = [1 1]; B = 62; lb = [0.25 50];

ub = [2 60];

[x fval] = fmincon(@pkoopt,x0,A,B, lb,ub)

The optimum/maximum value for groundnut oil

FAME yield was obtained as 100.5141 with the

corresponding independent variables (X1, X2) of

(0.25, 51.3463). On the other hand, the optimum/

maximum value for PKO FAME yield was gotten

as 90.7254 with the corresponding independent

variables (X1, X2) of (0.4843,50).

3.4.2.MATLAB response surface methodology

The surface plots with the contour of the groundnut

oil and PKO FAME model were plotted as indicated

in Figure 3.

0.5

1.5

-50

100

catalyst concentration (%)

X: 0.425

Y: 50

Z: 89.77

temperature (oC)

FAME yield (ml)

0.5

1.5

100

120

catalyst concentration (%)

X: 0.6

Y: 58

Z: 104.7

temperature (oC)

FAME yield (ml)

100

Fig. 3. Surface plot of the groundnut oil and PKO base

FAME showing the optimal points

Anal. Methods Environ. Chem. J. 5 (3) (2022) 55-69

4. Conclusion

The results obtained from this present study

showed that the optimum reaction conditions for

the production of biodiesel from groundnut oil and

palm kernel oil was obtained at a trans-esterication

temperature of 55oC, 0.5 % w/v of CH3ONa catalyst,

mixing rate of 360 rpm and a reaction time of 90

minutes. At these conditions, an optimum yield of

98% and 84% by volume of FAME from groundnut

and palm kernel oil was obtained. The biodiesel

produced in this present study was characterized for

fuel properties, and it gave good promising results;

except for the pour points of biodiesel produced from

palm kernel oil was found to be somewhat higher,

which may point to potential difculties in cold

starts and lter plugging trouble. But however, the

biodiesel from this experiment would be a better

means in harnessing the supply of energy to the global

economy as compared to mineral diesel. The 4th order

polynomial model showed a good agreement with

the experimental results, demonstrating that these

methodologies were useful for modelling. Newton

Raphson’s multivariable optimization technique

gave an optimum yield of 100.5 mL and 90.7 mL for

groundnut oil and PKO FAME with a corresponding

catalyst concentration and trans-esterication

temperatures of (0.25%, 0.48%) and (51.3oC, 50oC).

While the surface plots gave optimum yields of 104.8

mL and 89.8 mL with the catalyst concentration and

trans-esterication temperatures of (0.6%, 0.425%)

and (58oC, 50oC) for groundnut oil and Palm Kernel

Oil (PKO) based Fatty Acid Methyl Esters (FAME).

The ndings obtained from this study showed that

the Newton Raphson’s multivariable optimization

technique and Response Surface Methodology

(RSM) were useful in enhancing the process

parameters of the trans-esterication reaction.

5. Conict of interest and Abbreviations

No conict of interest to declare.

FAME: Fatty Acid Methyl Ester; PKO: Palm

Kernel Oil; ASTM: American Society of Testing

and Materials; KOH: Potassium Hydroxide;

NaOH: Sodium Hydroxide; CH3OH: Methanol;

H2SO4: Sulphuric Acid; RSM: Response Surface

Methodology; FFA: Free Fatty Acid; CH3Ona:

Sodium Methoxide.

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Anal. Methods Environ. Chem. J. 5 (3) (2022) 70-79

Research Article, Issue 3

Analytical Methods in Environmental Chemistry Journal

Journal home page: www.amecj.com/ir

AMECJ

Determination of cadmium in rice samples using

amino-functionalized metal-organic framework

by a pipette tip solid phase extraction

Mohammad Abbaszadeha, Ali Miria , and Mohammad Reza Rezaei Kahkha a,*

a Department of Environmental Health Engineering, Faculty of Health, Zabol University of Medical Sciences, Zabol, Iran

ABSTRACT

In this study, the amino-functionalized metal-organic framework

(NH2-MOFs) was used as an adsorbent for the extraction of cadmium

in rice samples based on the pipette tip solid phase extraction (PT-SPE)

before determined by the ame absorption spectrometry (F-AAS). The

pH of the sample solution, initial concentration of the cadmium, the

volume of the sample, elution conditions, and the amount of adsorbent

on the recovery of the cadmium were investigated and optimized.

The results showed that the best extraction efciency of cadmium

was obtained at pH 5.0, 2500.0 µL of cadmium solution, and 20.0

µL of HCl (10% V/V) as eluent solvent. First, the cooking rice was

transferred to a beaker and hydrochloric acid/nitric acid was added to

it as a digestion process before analysis by the PT-SPE procedure. The

limit of detection of this method was found to be 0.03 µg L-1 with a

relative standard deviation of ≤ 2.5 % (for seven replicate analyses of

50 µg L-1 of cadmium). The linear and dynamic ranges were achieved

at 0.3 -14.5 µg L-1 and 0.3 -150 µg L-1, respectively. The adsorption

capacity of sorbent and enrichment factor was 175 mg g-1 and 125

folds, respectively. The proposed method was successfully applied

for the determination of cadmium in rice samples.

Keywords:

Cadmium,

Amino functionalized metal-organic

framework,

Pipette tip extraction,

Rice samples,

Atomic adsorption spectrometer

ARTICLE INFO:

Received 21 May 2022

Revised form 2 Aug 2022

Accepted 28 Aug 2022

Available online 29 Sep 2022

*Corresponding Author: M. R. Rezaei Kahkha

Email: m.r.rezaei.k@gmail.com

https://doi.org/10.24200/amecj.v5.i03.208

1. Introduction

Pollution of foods with heavy metals (HMs)

is a serious problem for public health and the

community due to its toxicity and carcinogenicity.

Therefore, monitoring and controlling the amount

of HMs in food samples is critical. Cadmium is one

of the most dangerous HMs that enters food samples

from various sources, including mining, industrial

production and other ways such as agricultural

runoff [1]. According to the US Environmental

Protection Agency, the maximum acceptable level

of cadmium in rice and wheat is 200 µg. kg-1 [2].

On the other hand, the accumulation of cadmium

ions in food samples such as rice, wheat, and other

species is unavoidable[3]. In these food samples,

the effect of matrices is a serious problem for its

measuring because of the low concentration of

cadmium, therefore, a preconcentration technique

is necessary before quantication[4]. Various

techniques have been applied for this purpose such

as dispersive liquid- liquid microextraction [5],

cloud point extraction [6] and solid phase extraction

(SPE) [7]. The pipette tip (PT), a micro-scale

format of SPE, that used for the preconcentration

and extraction of various samples[8]. Using a

small amount of sorbent (insert into a pipette tip)

and low solvent consumption without a special

auxiliary device is the advantage of PT-SPE

compared to conventional SPE cartridges [9,10].

------------------------

Recently PT-SPE was applied for the determination

and extraction of several analytes in food samples

such as bisphenol a [11], estradiol in milk [12],

and antibiotic residues Metal-organic frameworks

(MOFs) are a new class of hybrid porous materials

consisting of organic linkers coordinated to

inorganic metal nodes that are used in solid phase

extraction because of their thermal and chemical

stability[14]. Recently, several adsorbents

such as silica nanoparticles [15], molecularly

imprinted polymer [16], and other sorbents were

applied for determination of cadmium in food

samples[17]. Hence, based on the above remarks

and our research interest in applications of porous

materials [18-21]we utilized the highly stable

amino functionalized metal organic framework

(Fig. 1) for the determination and extraction of

cadmium in imported rice samples. Many other

papers were presented about extraction methods

by previous researchers [22-24]. Parameters

affecting PT-SPE were studied and optimized.

To the best of our knowledge, the MOF with the

properties mentioned above was applied for the

rst time as a solid phase sorbent in a pipette-tip

microextraction mode.

2. Material and methods

2.1. Reagents and instrument

All reagents and solutions were analytical grades.

Methyl 4-formylbenzoate (CAS N: 1571-080 ,

Sigma, Germany), pyrrole (CAS N: 109-97-7, pH

>6, Merck), the triuoroaceticacid (CAS N: 76-

05-1, EC Number 200-929-3, TFA) from Sigma-

Aldrich, propionic acid (CAS N: 79-09-4, MW:

74.08, Sigma-Aldrich), ZrOCl2•8H2O (CAS N.:

13520-92-8, 98%, Sigma-Aldrich), 1000 mg.L-1

standard solution of cadmium (CAS N: 7440-43-9

Sharlou, Spain), N,N′-dimethylformamide (CAS N:

68-12-2, DMF), benzoic acid (>98%, CAS N: 65-

85-0; EC N: 200-618-2, Sigma), acetone ( ≥99.5%;

CAS N: 67-64-1, Sigma, Germany), tetrahydrofuran

(THF, CAS N: 109-99-9 EC N: 203-726-8, Sigma),

methanol (CAS N: 67-56-1), and KOH (CAS N:

1310-58-3, Sigma, Germany) were purchased from

commercial sources and used as received. The

ame atomic absorption spectrometer based on a

double beam spectrophotometer (FAAS, AA7800,

Shimadzu, Japan) was used for cadmium detection

The mixture of C2H2 gas and the D2 was tuned for

the cadmium determination by FAAS.

Determination of Cadmium in Rice by NH2-MOFs Mohammad Abbaszadeh et al

Fig.1. A schematic of amino functionalized MOF.

2.2. Synthesis of amino-functionalized metal-

organic framework

The sorbent was synthesized in a similar way that

we have previously reported [25]. Briey, 200 mg

of ZrOCl2•8H2O, 3.0 g of benzoic acid, and 20 mL

of DMF were added into a 30-mL vial (solution

A); and in other 30- mL vial, 100 mg of H2TCPP

and 20 mL of DMF were added (solution B). Both

solutions A and B were sonicated for 30 min and

then incubated at 100 °C in an oven for 1 h. Next,

1 mL of A solution, 1 mL of B solution, and 0.05

mL of triuoroacetic acid were added and mixed

by swirling for 5 s. The vials were then incubated

and immersed in an oven at 120 °C for 30 h. A dark

purple precipitate started to form in the vials. After

cooling to room temperature, the suspension was

transferred into a centrifuge tube and centrifuged

for 5 min (7500 rpm) to remove the supernatant.

The solid was washed with fresh DMF (330 mL)

before soaking in 40 mL of fresh DMF and 1.5 mL

of 8 M HCl (activation with HCl). It was then heated

at 120 °C for 12 h to remove the benzoic acid. The

sample was subsequently washed with fresh DMF

(330 mL), THF (330 mL), and acetone (330

mL). After soaking in acetone overnight, the solid

was collected, and then dried in a vacuum oven

at 120 °C for 12 h to give the MOF. SEM of the

amino-functionalized metal-organic framework is

seen in Figure 2.

2.3. Pipette-tip extraction procedure

Appropriate amounts of sorbent were inserted into

a pipette-tip (DRAGON, China) which was then

attached to a 5000 µL micro pipette (DRAGON LAB,

China). Then 2500 µL of the aqueous sample was

withdrawn into the sorbent and dispensed back into

the same tube for 20 cycles. Elusion was performed

by 20 µL of 10%HCl into a 1-mL vial. The desorption

step was also performed by 20 aspirating/dispensing

cycles. The extraction recovery of cadmium was

calculated by comparing the absorbance of 50 µg

L-1 of cadmium standard solution by results of

optimization experiments (Fig.3).

3. Results and discussion

3.1. Optimization of affecting parameter on the

extraction procedure

To optimize the extraction conditions, parameters

affecting extraction were optimized as below. All

optimizations were performed on a 50 µg L-1 of

cadmium solution, made by diluting of 1000 mg

L-1 standard solution.

Anal. Methods Environ. Chem. J. 5 (3) (2022) 70-79

Fig.2. SEM images of synthesized NH2-MOFs

3.1.1.Effect of pH

The effect of sample pH on the extraction efciency

of cadmium was investigated by adjusting pH of it

between 2.0 and 9.0. Either 0.1 M NaOH or 0.1 M HCl

was used. As depicted in Figure 4, a solution with the

pH values between 4.0 and 6.0 showed the highest

extraction efciency (optimal pH = 5). In alkaline

media, produced hydroxide ions can form a complex

with cadmium ions, and a precipitation (Cd(OH)2) is

created. Results showed that the extraction efciency

of cadmium based on NH2-MOFs was decreased. So,

pH 5.0 was selected as the optimum value.

Determination of Cadmium in Rice by NH2-MOFs Mohammad Abbaszadeh et al

Fig.3. Cadmium extraction based on NH2-MOFs adsorbent and Pipette-tip- SPE procedure

Fig. 4. Effect of pH on recovery of cadmium

3.1.2.Effect of amount of sorbent

To obtain the best extraction efciency and good

recoveries of cadmium ions, the amount of sorbent

was examined between 1-5 mg. The adsorption

ability of the adsorbent was increased by increasing

the amount of sorbent up to 2 mg; therefore, the

optimum amount of 2 mg was chosen (Fig. 5).

3.1.3.Effect of volume of the eluting solvent

Several strong acidic solvents including different

concentrations of HNO3 (2-10% V/V) and HCl

(2-10% V/V) were studied to select an optimized

eluting solvent. Among them HCl 10% showed the

highest extraction efciency for cadmium ions. To

achieve the highest enrichment factor, we tried to

obtain the smallest HCl volume of 10%. Volumes

between 5 to 50 µL of HCl 10% were examined

for the extraction of 1000 µL of a standard solution

containing 50 μg L-1 of the cadmium in deionized

water. As shown in Figure 6, at the volume of 20

µL of the eluting solvent, the recovery of cadmium

is at its highest value.

Therefore, the eluting volume of 20 µL was

selected for further experiments.

3.1.4.Effect of volume of sample solution

Amount of sample solution taken for the analysis is

an important parameter in solid phase extraction [5].

Different volumes of sample solution were tested at

the range of 200 to 4000 µL containing 50 µg L-1 of

cadmium. As can be seen in Figure 7, the extraction

recovery of cadmium increased with the increase

of the volume up to 2500 µL. So, the extraction

efciency (more than 95%) and a preconcentration

factor of 125 for cadmium extraction were achieved

based on 20 μL of eluent with the PT-SPE procedure

before determination by the F-AAS.

3.1.5.Effect of number of aspirating/dispensing

of sample and elution solvent

The number of aspirating/dispensing cycles of

eluent solvent and the volume of solution that passed

through the extractor resembles the extraction

time. The results showed the highest recoveries

Anal. Methods Environ. Chem. J. 5 (3) (2022) 70-79

Fig. 5. Effect of amount of sorbent on recovery of cadmium.

Determination of Cadmium in Rice by NH2-MOFs Mohammad Abbaszadeh et al

Fig. 6. Effect of volume of eluting solvent (HCl 10%) on recovery of cadmium

Fig. 7. Effect of sample volume on recovery of cadmium

for cadmium obtained at 20 cycles, when 2500 µL

of a sample containing 50 µg L-1 of the standard

solution was used. During desorption, the analyte

was eluted from the extractor into a 2.0 mL glass

test tube by repetitive aspirating/dispensing of 20

µL of the HCl 10% (V/V) through the tip. The

optimal number of aspirating/dispensing cycles

for desorption of adsorbed analytes (provided the

highest recovery) was found to be 20 cycles at

12min.

3.1.6.Reusability of the adsorbent

The reusability of the sorbent was investigated by

washing of the column with HCl 10% V/V and then

ve cycles with deionized water. After that, several

extraction and elution operation cycles were carried

out under the optimized conditions. The results

indicated that the amino functionalized MOF could

be regenerated and reused at least ten times without

signicantly decreasing extraction recoveries.

3.1.7.Sorption capacity

To investigate of the adsorption capacity of the

functionalized MOF, a standard solution containing

100 mg L−1 of cadmium ions was applied. The

maximum sorption capacity is dened as the total

amount of cadmium ions adsorbed per gram of the

sorbent. The obtained capacity of the adsorbent

was found to be 175 mg g−1.

3.1.8.Effect of interfering ions

The effect of common co-existing ions that often

companion with cadmium ions in real samples on

cadmium determination was studied in optimum

conditions by analyzing 100 μg L−1 of cadmium

after addition of varying concentrations of Na+,

K+, Ca2+, Cu2+, Zn2+, Ni2+, Mn2+, and Fe2+. The

concentration ratio of other ions was as follow:

1750 for Na+, K+; 1500 for Ca2+, Mg2+; 1250 for

Cu2+, Zn2+, Fe2+, Ni2+, Mn2 +. Results showed that

interference ions do not inuence on extraction

recovery of cadmium. Hence, the method was

selective for preconcentration and extraction of

cadmium (Table 1).

3.2. Analytical performance of suggested method

The analytical performance of the suggested

pipette-tip solid phase extraction was evaluated, and

the results are summarized in Table 2. The limit of

detection (LOD) was obtained based on a signal-to-

noise ratio of 3. The linearity range was studied by

varying the concentration of the standard solution

from 0.3 to 150 µg L-1. The repeatability of the

method, expressed as relative standard deviation

(RSD), was calculated for seven replicates of the

standard at an intermediate concentration (50 μg

L-1) of the calibration curve. The precision of the

method was determined by repeatability (intraday

precision) and intermediate precision (inter-day

precision) of both standard and sample solutions.

Anal. Methods Environ. Chem. J. 5 (3) (2022) 70-79

Table 1. The effect of interfering ions on the recovery of Cd (II) ions in water samples

by PT-SPE procedure coupled to F-AAS

Interfering Ions(M)

Mean ratio

(CM/CCd) Recovery (%)

Cd(II) Cd(II)

Al3+ 750 97.5

Na+, K+1750 97.8

Cu2+, Zn2+, Fe2+, Ni2+, Mn2 + 1250 98.2

I- , Br-, F- 1100 97.7

Ca2+, Mg2+ 1500 98.0

Co2+, Pb2+ 950 97.9

Ag+, Au3+ 250 96.5

Precision was determined in seven replicates of

both cadmium standard solution (100 μg L−1) and

sample solution (100 μg L−1) on the same day

(intra-day precision) and daily for 8 times over

a period of one week (inter-day precision). The

results are represented as % RSD and indicated

that intra-day precision and inter-day precision of

the method were 5.0% and 3.5%, respectively.

3.3. Determination and validation of cadmium

in rice samples

Rice samples were purchased from several local

markets. About 50 gr of rice was weighed and

cooked in the oven for 8 hours at the temperature

is 80 o C with the aim of removing moisture

and determining weight It was dry. After drying

and reaching constant weight, 10 gr of rice was

transferred to a 250.0 ml beaker Samples for 48

hours at a temperature of 105o C it placed. Then

5 ml of 37% hydrochloric acid and 15 ml of 65%

nitric acid were added to them and after 120

minutes at the laboratory temperature, it dissolved

slowly and heated until its volume reached less

than 20 ml. Then the obtained clear solution was

cooled, ltered and used for the determination

of cadmium according to the above PT-SPE

method. As can be seen in Table 3 concentrations

of cadmium in all samples in comparison to

the maximum acceptable level (200 µg g-1) are

adequate.

Determination of Cadmium in Rice by NH2-MOFs Mohammad Abbaszadeh et al

Table 2. Analytical gures of merit for proposed methods

Parameter Analytical feature

Dynamic range (μg L-1) 0.3 -150

R2 (determination coefcient) 0.99

Repeatability (RSD a %) 2.45

Limit of detectionb (ng.L-1) 15

Enrichment factor (fold) 125

Total extraction time (min) ≤ 12

aRSD, relative standard deviation, for 5 replicate measurements of 50 µg.L-1 of the analyte

bLimit of detection was calculated based on the 3Sb/m criterion for 10 blank measurements

Table 3. Determination of cadmium in different rice samples under optimized conditionsa

Rice Sample Added

(µg g-1)

Found

(µg g-1)

Recovery

( %)

RSD %

(n=3)

0 45 - -

50 94.2 98.2 2.7

150 194.5 74.3 3.2

0 40 - -

50 89.3 98.7 1.7

100 139.2 98.1 2.8

0 55 - -

50 104.7 98.7 3.6

100 154.5 98.5 2.8

aThe maximum acceptable level of cadmium in the rice reported by WHO is 200 µg g-1

78 Anal. Methods Environ. Chem. J. 5 (3) (2022) 70-79

4. Conclusion

In this research, for the rst time, we employed an

amino functionalized MOF with a high surface area and

large porosity for PT-SPE of cadmium. This method

is very simple, fast, solvent-free and applicable for

the extraction of cadmium. The total time of analysis,

was less than 12 minutes and the functionalized-MOF

sorbent was used for at least 10 extractions without any

change in its capacity. Only 2mg of the sorbent was

enough to ll the PT. Moreover, evaluation of intra-

day and inter-day showed a notable precision with

RSD below 5 and 3.5%, respectively. This method

was applied successfully for the determination of

cadmium in three rice samples. Real samples spiked

with three concentration levels and results indicated

that sorbent can be applied in the complicated matrix

for analysis of heavy metals such as cadmium. Also,

analysis of real samples showed that the concentration

of cadmium in all samples is below the acceptable

range.

5. Conict of Interest and Ethical approval

The authors have declared no conict of interest.

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Anal. Methods Environ. Chem. J. 5 (3) (2022) 80-102

Research Article, Issue 3

Analytical Methods in Environmental Chemistry Journal

Journal home page: www.amecj.com/ir

AMECJ

A review: Total vaporization solid-phase microextraction

procedure in different matrixes

Yunes M. M. A. Alsayadi a,*, and Saahil Arorab

a University Institute of Pharmaceutical Sciences, Chandigarh University, Punjab-140413, India

b University Institute of Pharmaceutical Sciences, Chandigarh University, Punjab-140413, India

ABSTRACT

Total vaporization solid-phase microextraction (TV-SPME) is a type

of extraction technique in which a specic solvent dissolves the

analyte. Then a tiny amount of solvent is taken to the vial of SPME.

Then, the solvent vaporizes in the SPME vial, and sampling is carried

out on the headspace of the SPME ber. As a result, the partitioning

phase of the analyte between the headspace and liquid sample is

omitted. The equilibrium phase remains the analyte partitioning

between the headspace and SPME. TV-SPME was introduced in

2014 by Goodpaster to increase the recovery compared to the liquid

injection method. This review discusses different aspects of TV-

SPME, including its impact on sampling techniques, theoretical part,

sampling procedure, and method optimization. Special attention

was paid to its applications. A comprehensive literature study was

conducted in the relevant databases to summarize the research

work that has been done on this technique. In TV-SPME, the liquid

samples completely vaporized and had a less matrix effect and better

adsorption. This method needs no sample preparation, consumes less

supply, and can be done automatically. Also, TV-SPME enables a cost-

effective and efcient extraction for different matrixes. This review

summarizes aspects related to TV-SPME including its sampling

procedure, method optimization, and its preference for conventional

liquid methods. Special attention was paid to its applications of the

vacuum-assisted total vaporization solid-phase microextraction

procedure (VA-TV-SPME).

Keywords:

Solid-phase microextraction,

Headspace solid-phase microextraction,

Total vaporization solid-phase

microextraction,

Vacuum-assisted total vaporization

solid-phase microextraction,

Method optimization

ARTICLE INFO:

Received 21 May 2022

Revised form 2 Aug 2022

Accepted 28 Aug 2022

Available online 29 Sep 2022

*Corresponding Author: Yunes M. M. A. Alsayadi

Email: yunes20171@gmail.com

https://doi.org/10.24200/amecj.v5.i03.190

1. Introduction

Solid-phase microextraction technique (SPME) is

widely used for pre-concentration/separation of

analyte from the sample, analytes are absorbed on

a ber and then, it desorbed before determined by

analytical instrument such as GC-FID [1,2]. SPME

was introduced in 1989, and since then, it has been

used extensively in the eld of environmental

chemistry, with more than 1500 publications. SPME

is a technique with off-column pre-concentration

sampling that facilitates the trace analysis of the

occurring abundance of matrices and samples. This

technique depends on a polymer ber with surface

chemistry designed to increase targeted compounds’

adsorption [3, 4, 5]. SPME was initially presented as

a solvent-free technique combining the prepared

sample into one-step sampling, sample introduction

extraction, and concentration [1,6]. Two processes

are involved in the SPME extraction: (1) the

analytes partitioning between the ber coating and

the sample, and (2) the desorption process occurs

by the concentrated analytes from the coated ber

------------------------

A review: Total vaporization solid-phase microextraction Yunes M. M. A. Alsayadi et al

to the instrument to be used for the analysis. The

extraction is performed by placing a solid sample

containing volatile analytes and an aqueous sample

containing organic analytes into a vial, then closed

with a septum and cap [7]. The main advantages

of SPME are a simple extraction method, efcient,

selective, and fast. SPME followed with less amount

of sample volumes and no-solvent consumption.

For those advantages, it was implemented quickly

in many disciplines of analytical chemistry, like

bioanalysis, environmental science, and chemical

analysis [8,9,10]. In addition, SPME can be

coupled and automated with instruments like

gas chromatography, which easily estimates the

organic compound [11]. Direct analysis of complex

matrixes mostly cannot be performed in a manner

that attains the sensitivity and selectivity needed

for many trace analysis applications. To solve

this issue, SPME techniques were used so that

preconcentrating of analytes occurs selectively

before placing it into ion trap mass spectrometric/

gas chromatographic analysis. This approach was

introduced to be used in the trace analysis of the

metabolites of explosives in seawater [6]. The SPME

technique includes exposing a ber of fused silica

coated with a solid phase to an aqueous solution

containing organic compounds [12]. It involves

using a silica ber coated with a polymer lm to

adsorb compounds of interest from their matrices.

Such a technique is a solvent-free, reliable, and

inexpensive method that can be used practically

for aqueous sample analysis/headspace and shows

good sensitivity and excellent selectivity [13]. The

SPME technique is used for multiple sampling, and

sample preservation leads to minimizing the risk of

contamination of the sample because the technique

affords a simplied sample handling [14]. SPME is

mainly carried out in one of the two modes; either

headspace or immersion technique. In headspace

SPME mode, the extraction of analytes by bers

occurs from the headspace above a sample. While in

immersion SPME mode, the extraction of analytes

by the ber takes place directly from a liquid

sample [15]. In headspace SPME, the partition of

analytes occurs between the headspace above the

sample and the coating ber of SPME [16,17]. The

main criteria for applying headspace solid-phase

microextraction (HS-SPME) was to prevent the

ber of SPME coatings from being tricked by the

components of sample matrices [18]. In HS-SPME,

the ber is placed into the vial of the sample, the

volatile organic compounds that are available in

the headspace, are bound to the coating, and then

the ber is to be taken to the site of injection of

the Gas Chromatography (GC) for desorption and

further analysis [13] HS-SPME compounds having

analytes with low volatility from complex aqueous

samples can be used by the manner of increasing

the temperature of the sample. Still, some SPME

coatings made from some adsorbent substances

may face difculties due to their low stabilities,

particularly in a hot medium like a steam of hot

water. It is the preparation of super hydrophobic

metal-organic framework (MOF) that is obtained

from decoration nodes of the amino-functionalized

UiO-66(Zr) with phenyl silane was needed and then

successfully improved to be used in a novel ber

coating of SPME [15]. The scientists of food avors

have appreciated the ease of use and sensitivity

of the headspace technique mode by using it in

analyzing the volatile compounds in many food

products [19]. Headspace SPME sampling was

widely used in analyzing of some intact explosives

like triacetone triperoxide (TATP) which was

detected from headspace applying planar SPME

with the help of an ion mobility spectrometer[20].

HS-SPME is a pre-sampling technique that does not

need complicated apparatus or solvents [21]. HS-

SPME can integrate the concentration, extraction,

and introduction in a single step. Combing HS-

SPME with GC–MS is employed to determine

the volatile components in different plants like tea

samples [22]. In the immersion SPME sampling

technique, the ber is directly placed into a liquid

sample and the compounds of interest absorb/

adsorb to the ber coating. After the absorption/

adsorption, the ber is then placed for desorption

in the inlet of a LC or GC for further analysis

[23]. Immersion SPME sampling has been utilized

practically in the applications of environmental

82 Anal. Methods Environ. Chem. J. 5 (3) (2022) 80-102

studies for extracting organic explosives that are

present in aqueous soil extracts and/or water to be

later analyzed by GC-MS and GC-electron capture

detection [6,16]. Some explosives examples that

have been detected and recognized in this method

like PETN, 2,6-dinitrotoluene, RDX (composition

C-4), TNT, and NG (dynamite) [24,25]. Both the

techniques either headspace or immersion SPME

cannot be smoothly applied to the detection and

identication of some explosive residues especially

those present on post-blast debris, regardless of

many previously reported descriptions of its unique

use, for example, the detection of a single particle

of smokeless powder [2] or the residue extraction

of the explosives that obtained from soil samples

collected from the blast site after an explosion

[25,26]. In fact, headspace and immersion SPME

methods have been used to analyze a various

analytes [27]. TV-SPME is almost a new technique

that is being utilized in analytical chemistry. It is

always in comparison with conventional techniques

including HS-SPME in the motive of determination

of the superior technique. That comparison is

highly appreciated as it plays a critical turn in the

superiority of the method that is to be adopted.

And in the case of TV-SPME and HS-SPME, it is

important to compare them to see if one is superior,

as it helps to choose a method with specic samples

[28]. These two methods are among the advanced

micro extraction methods as they require least to

almost no sample preparation compared to other

liquid methods which require a high amount of

the sample [29]. They involve placing the samples

directly into the headspace in place of placing them

to do individual extraction techniques to a sample

ahead of being directly injected into the GC. Table

.01 shows the differences between the HS-SPME

and TV-SPME [30]. The comparison concentrates

on the sample volumes, analysis time, and matrix

effects as these parameters are critical for analysis

samples.

Environmentally, TV-SPME has been used to

analyze drugs and their metabolites in saliva,

urine, and hair. This valuable simple technique

has also been used in analyzing lipids, fuel

samples, street drugs, lipids, and pollutants in

water and post-blast explosive residues [30],

[33], [36-38]. TV-SPME has been used to identify

illegal adulterants in tiny samples (microliter

quantities) of alcoholic beverages [39-40].

Both gamma-butyrolactone (GBL) and gamma-

hydroxybutyrate (GHB) were identied at levels

that would be found in spiked drinks [34]. There

were techniques being used, including Membrane

protected micro-solid-phase extraction (µ-SPE),

which was used for the rst time in 2006 with the

motive of replacing multistep SPE. The principle

of µ-SPE lies in taking a minimal amount of the

sorbent and packing it inside a porous membrane

paper having edges that are heat sealed for the

fabrication of a µ-SPE device. This device can

perform pre-concentration and extraction in a

single step. Such techniques seem to have the

best extracting method, especially for complex

Table 1. Differences between the HS-SPME and TV-SPME

Parameter HS-SPME TV-SPME

Sample volumes Sample utilization is at least 1mL.[29,31-33].**Almost 1 µl - 100 µl as TV-SPME vaporizes the

sample completely [31,34].

Matrix effect The effect of matrix is higher as it is between two

phases only [32, 33].

less matrix effects are there as it results in fully

vaporizing the analyte and its matrix[34].

Analysis time.

***HS-SPME and other liquid injection, need that

the analyte to be reacted with the derivatizing agent

in solution [33, 35].

As TVSPME allows for the analyte to be derivatized

during the extraction process which reduces analysis

time [27, 34].

**Almost 1 µl - 100 µl as TV-SPME vaporizes the sample completely, analyte partitioning will be there between the vapor and only

the ber, which lead forcing more amount of the sample to adsorb into the ber and large amount of the sample can be exposed to

the vapor. And that can cause minimizing the sample size [31,34].

***Other methods including HS-SPME and other liquid injections, need that the analyte to be reacted with the derivatizing agent

in solution prior to being injected into the GC. And that lead to minimize the time of analysis[33, 35].

A review: Total vaporization solid-phase microextraction Yunes M. M. A. Alsayadi et al

samples, since extraneous matter does not adsorb

over the sorbent as it is protected effectively inside

the Membrane [39]. Direct Immersion-Solid

Phase Microextraction (DI-SPME) is preferred

for aqueous samples as the ber is introduced

directly to the sample solution. However, when

applied to a complex matrix, the sample must be

pretreated; otherwise, some interfering substances

from the matrix can bind irreversibly to the ber.

As a result, choosing the mode is not preferred in

the case of complex samples, including samples

arising from food, sludge, and biological origin

[39-40]. To overcome such issues, HS-SPME can

be used, although it has some limitations, including

it can work better only for volatile compounds and

that compounds having good volatility even with

almost moderate heat. Therefore, nonvolatile or

low volatile compounds cannot be extracted by

applying such an approach. So, something should

be developed for extracting compounds with less

or no volatility from complex samples by adopting

a mode of direct immersion [41]. Differences

between DI-SPME, HS-SPME, and Membrane

Protected SPME, are shown in Figures 1 (a and b).

Fig. 1b. DI-SPME, HS-SPME and membrane protected SPME

Fig. 1a. DI-SPME, HS-SPME and membrane protected SPME

84 Anal. Methods Environ. Chem. J. 5 (3) (2022) 80-102

SPME and its derivative techniques are a well-

recognized method of extraction which utilize zero

solvents and has a wide scope and applications,

including biomedical, food, forensic, and

environment [35,41]. Moreover, they can be applied

in organic contaminants extraction like; pesticides,

Pharmaceutical compounds, emerging pollutants,

and persistent organic pollutants [42-53]. Total

vaporization (TV) is a technique that can be

practically utilized in conjunction fused with

headspace sampling. The residual solvents will

be released from the matrix by applying TV to a

solid sample. Furthermore, applying it to the liquid

samples allows the whole sample to be vaporized

before the headspace sampling [54]. TV technique

applies to many samples like solid samples (e.g.,

residual solvents), [55], aqueous solutions (e.g.,

odor compounds) [56] and fermentation liquor

(e.g. ethanol) [57]. The approach of coupling TV

and SPME (TV-SPME) offered great sensitivity

and even low detection limits for compounds

present in the hair of some users of tobacco such as

nicotine and cotinine. In the TV-SPME technique,

a sample extract needs to be heated until it gets

vaporized and ber of SPME is utilized for pre-

concentrating analytes from the produced vapor

[53]. In TV-SPME, a complete vaporing of the

liquid samples gives a fewer matrix effect and

better adsorption. This method does not need

any sample preparation, utilizes less supplies

and can be done automatically, enabling it to be

both a cost-effective and efcient method [58].

SPME is a sensitive technique where the liquid

portion is totality vaporized before being placed

for sampling, easing to attain equilibria inside the

sample vial and increasing the analyte’s availability

in the headspace, leading to making the analyte

quantity more [53,59]. TV-SPME is an effective

technique that does not require derivatization while

being used to analyze controlled substances, either

with or without on-ber. Total vaporization is a

technique that has been utilized in simple headspace

sampling. Still, matrix effects that result between

two phases in headspace sampling are a matter of

concern. One important method to remove matrix

effects is completely evaporating the analyte

and its matrix. Total vaporization headspace is

applicable in determining ethanol in fermentation

liquor, methanol in wood pulp, odor compounds in

aqueous samples, and volatile organic compounds

in biological samples [56,60-62]. The matrix

effects in SPME can be eliminated by extracting

analytes (quantitatively) from complex matrixes.

This method is known as cooled ber SPME, and it

has been applied for extracting polycyclic aromatic

hydrocarbons (PAHs) from heated soil samples

[3]. Also, the urine extracts in solvent and have

been evaporated in a headspace vial. The residue

was heated until analytes derivatize, vaporize, and

absorb to a SPME ber [63].

2. Experimental

2.1. TV-SPME sampling procedure and practical TIPs

SPME ber format was one of the most commonly

used forms of the technique for many years [64]. In

SPME ber format, a small amount of the extracted

phase is coated by a thin and short fused-silica rod,

which is revealed for a specic time directly to the

headspace above the sample or to the sample itself.

Analytes of interest were taken from the sample to

be analyzed in the SPME ber coating, and then

the sample was extracted till the point when the

quantity of analyte extracted by the ber remained

constant even if the sampling time increased i.e., the

analyte concentration attained partition equilibrium

state between the ber coating and sample [65].

Generally, the time needed to attain equilibrium

relies on the characteristics of the ber coating,

matrix, and target analyte, and its range varies

from a few minutes to many hours [66]. SPME

sampling includes two stages of the equilibrium

mechanism, which occur between the headspace/

sample (first stage) and the fiber coating/

headspace (second stage). In the TV-SPME

technique, the equilibrium process between the

sample/headspace is no longer needed since the

analytes can be directly partitioned from the fiber

coating and headspace [67]. Figure 2 shows the

sample preparation of HS-SPME and TV-SPME.

For HS-SPME, the extraction of volatile analytes

A review: Total vaporization solid-phase microextraction Yunes M. M. A. Alsayadi et al

is noticed to happen faster than analytes with

semi volatiles nature [15]. For that, the longer

equilibration times could be less in various ways,

including agitating the sample, heating the sample,

maximizing the headspace/sample interface, and

implementing the cold ber HS-SPME proposal

to cool the ber coating and heating the sample

matrix occurs simultaneously [13]. The effects

of the matrix that can be produced between two

phases while sampling in the headspace technique

is a matter of concern. An important method to

remove such effects from the matrix is applying

heat to evaporate the analyte and its matrix fully. An

excellent example of the use of total vaporization

headspace involves estimation of volatile organic

compounds in biological samples, methanol in

wood pulp, odor compounds in aqueous samples,

and ethanol in fermentation liquor [27]. In TV-

SPME, the extracted aliquot of the sample is

sentenced for heating till the point where both the

analytes and solvent are completely vaporized; after

that, the analytes partition between the SPME ber

and the vapor phase [16]. TV-SPME extraction of

analytes from a sample of interest was performed by

applying a specic solvent in this approach. Then,

a small part of this extract is fully vaporized inside

a headspace vial inserted into an SPME ber. Also,

the VOCs in water samples based on ber coating

on the needle were determined after HS-SPME and

TV-SPME were coupled to the GC-MS (Fig.3).

Fig. 2. Samples preparation of HS-SPME and TV-SPME

Fig.3. Determination VOCs in water samples based on ber coating on needle

after HS-SPME and TV-SPME coupled to the GC-MS

86 Anal. Methods Environ. Chem. J. 5 (3) (2022) 80-102

These results are a simple two-phase system.

In particular, patterns occur when the analytes

partition between the extract and the headspace is

removed and when the analyte partitioning occurs

directly between the vapor phase and the SPME

ber. In general, combining the total vaporization

technique with SPME increase preconcentrating

analytes onto the ber. For example, the estimation

of an organic analyte in an organic solvent is not

accessible by either immersion or headspace

SPME. For that, the solvent should get vaporized

and the analyte absorbed into the ber of SPME.

So, when the analyte gets distributed (in TV-

SPME) at a solid/vapor interface, it has been found

that the extraction time is less important than the

sample volume and extraction temperature for the

analytes to be recovered efciently. In TV-SPME,

extracts of the sample do not have to get ltered,

which gives it a signicant advantage compared

to liquid injection. Nonvolatile compounds or

solids that may have the chance to be laid within

an extract of the sample will stay on the surface

of the vial. That may lead to minimize extensively

the contamination and the quantity of buildup that

may take place in the inlet and the column of GC.

Furthermore, the boiling point of the analytes plays

an essential role in the selectivity of the GC inlet

in liquid injection. TV-SPME can add a level of

chemical selectivity because of the advantage of

the ber that can enable it to select the targeted

analyte specically. Finally, the volumes for the

liquid injection are almost 1 to 2 μL; thus, only

a tiny portion of the sample extract is needed for

the injection. The Large-volume injection (LVI)

techniques have thus been developed to be used

in the GC. However, LVI needs some changes

to meet the requirements for the instrument and

other analysis parameters. So, TV-SPME needs no

modication in instruments and other parameters,

enabling the use of large volumes of the sample for

the analysis in GC, which ultimately concluded

in great sensitivity over the liquid injection [27].

The idea of combining total vaporization with

SPME is almost similar to that of LVI techniques

in those large volumes of the sample (e.g., 200

mL) which lead to an increase the sensitivity.

However, TV-SPME is an essential technique

because it does not require any modication in the

GC instrument, such as exits for solvent vapor or

adding retention gaps.

Additionally, the sample extracts require no

ltration as any non-volatile or volatile components

oat above and within the surface of the vial. A

critical feature of TV-SPME is that although it

evaporates the liquid sample completely, resulting

in a much larger volume, it plays a vital role in pre-

concentrating the analytes more than compensates

for this dilution. In addition, a clear choice of

ber chemistry used in SPME can add remarkable

selectivity to the analysis [16].

2.2. TV-SPME method optimization

HS-SPME is a process of multi-stage equilibrium

[68] where the extracted analytes in the headspace

partition with the adsorptive surface on the ber

after the compounds get extracted from the matrix

to the sample headspace by the help of some

external force, including ultrasound, agitation

and rising the temperature. These strategies

shorten the time needed to attain equilibrium.

In 2014, a novel separation technique was

introduced by Goodpaster in which sampling

was to be performed only in the headspace [53].

In this technique, the extraction of the analyte

occurs by a solvent. Then a tiny amount of

the solvent is taken to the SPME vial by total

vaporization of the transferred solvent in the vial

used in SPME, and sample processing is taken

place on the SPME ber from the headspace [23].

Therefore, the phase of partitioning the analyte

extracts between the headspace and liquid sample

is omitted, and the only equilibrium phase that

remains is the partitioning of the analyte between

the headspace and SPME [69]. Reecting that

the partitioning process of the analyte is to occur

between the vapor and solid, it was noticed that

in comparison with extraction temperature and

sample volume, the extraction time parameter has

less signicance [67]. In addition, all non-volatile

and solid compounds stay on the surface of the

A review: Total vaporization solid-phase microextraction Yunes M. M. A. Alsayadi et al

SPME vial and are not taken to the injection

portion or the GC column. Therefore, it reduces

contamination in GC, and the sample extracts

require no ltration [16]. Also, the evaporation

of the sample is almost more, and a proper ber

of SPME is used for the preconcentration of

the analytes to enable the TV-SPME technique

to have a greater sensitivity compared to the

traditional SPME [69]. The TV-SPME method

depended on the vaporization of the total portions

of the sample, containing volatile, non-volatile,

and semi-volatile components. Therefore, it

is noticed that semi-volatile and non-volatile

compounds require more heat, and the sample

volume needed is a more signicant amount.

Consequently, it was reported that the SPME ber

is heated and that heat does not cause any fault

in the absorption of the analytes on the SPME

ber [67]. Maybe this is one of the limitation

factors, but it is considered to be among the main

reasons why this valuable technique is not more

widely used. As a result, few publications based

on TV-SPME have been written [70]. The TV-

SPME technique should be coupled with another

method to ease the vaporization; surpassing the

preparation steps and minimizing the required

heat would be helpful [71]. Various factors

must be investigated and optimized, such as the

desorption temperature, the extraction time and

temperature, and the salt concentration. Such

factors signicantly affect thermal desorption

and extraction efciencies [15]. For controlled

substances that are not thermally stable and

not sufciently volatile while being analyzed

by GC-MS, derivatization is used to improve

their characteristics to match the required

conditions in the method optimization in GC-

MS. The performance of GC-MS is signicantly

improved by the use of such derivatizing

compounds [71]. Although derivatization has

many benets, techniques of the conventional

solution phase work are time-consuming and

intensive. However, derivatization was adapted

to a sampling technique that is called TV-SPME

to automate and simplify the process. SPME is

a technique in which the analytes of interest are

placed for pre-concentration onto a ber coated

in adsorptive or absorptive material. TV-SPME

is a unique and novel technique in which a tiny

amount of solution is poured into a vial and heated

until complete vaporization occurs [53]. A ber

of SPME is then introduced, and the adsorption

of the sample onto the ber coating takes place.

TV-SPME belongs to immersion SPME in that

both are two-phase systems which differ from

headspace SPME, which is a three-phase system

[69]. Calculating the maximum volume for total

vaporization of a given solvent can be easily

obtained by the vial volume, molecular weight,

solvent vapor pressure, and temperature [53].

For example, the calculated maximum volume of

methanol for total vaporization in a 20-mL vial at

60°C is 24 μL [53].

When TV-SPME is used for sampling, it can

be streamlined the process of derivatization by

enabling it to be taken place simultaneously with

the extraction step in a process called on-ber

derivatization (Fig.4). This On-ber derivatization

was used before in conjunction with immersion

or headspace SPME [72]. However, it could be

desirable to use the advantages brought by TV-

SPME to bear for on-ber derivatization. In the

process of derivatization on-ber with TV-SPME,

an SPME ber is introduced to the headspace

of a vial that contains a small aliquot of liquid

derivatization agent. The ber is then taken to the

heated headspace of a vial that contains the sample.

The reaction between the derivatization agent

and analyte takes place directly in the headspace

surrounding the ber or on the SPME ber. After

sufcient time for adsorption and reaction, the

ber is taken to the inlet of the GC for desorption.

The use of an autosampler can make this a fully

automated process wherein the only sample prep

necessary is to dissolve the sample in a suitable

solvent and place an aliquot into the vial [73].

Several parameters are in direct touch with TV-

SPME method, involving desorption time, SPME

ber type, extraction time, sample volume and

desorption temperature [16,69].

88 Anal. Methods Environ. Chem. J. 5 (3) (2022) 80-102

2.3. TV-SPME based on liquid method

Although Gas Chromatography – Mass

Spectrometry (GC-MS) is considered to be

one of the most frequently used techniques in

the laboratories, it has some limitations since

compounds need to be volatile as well as thermally

stable. Without these two characteristics, GC-MS

cannot be used for regular routine analysis. For that

some compounds have to undergo derivatization

before injecting them into the gas chromatograph

(GC) to meet and satisfy these requirements of

thermostability and volatility. In SPME technique,

a sample is taken into a vial and then heat is applied

on the vial to initiate a site of the analyte to get

vaporized into the headspace. A polymeric material

such like polydimethylsiloxane-divinylbenzene

(PDMS/DVB) used to coat SPME ber, the coated

SPME ber is placed into the headspace of the

sample or immerged graphene-Fe3SO4–SPME

Fiber in water samples and the analyte is adsorbed

onto the ber concluding that the formation of a

thin coating of the analyte on the ber (Fig.5). The

ber is then introduced to the inlet of the GC for

desorption [74]. TV-SPME technique is almost

similar to that of headspace SPME but it differs by

the complete vaporization of a liquid sample prior

getting adsorbed onto the ber. Such adsorption

permits the occurrence of partitioning of the analyte

between only the coating of the ber and the vapor.

By this technique, more portion of the sample is

exposed for the adsorption onto the ber lead to

minimize the sizes of the sample (e.g., 1 – 200 μL)

can be utilized [75-76].

TV-SPME showed its ability to be an efcient

technique especially when used for the analysis

of controlled substances in both the ways

either with or without on-ber derivatization.

A summarized table for the results is presented

below: Table 2. Brief of results for TV-SPME and

liquid injection methods. + denotes that a single

chromatographic peak is formed. 0 denotes that

multiple chromatographic peaks are formed, and

– denotes that no any chromatographic peak is

formed [72,77].

even it could not be applied for all analytes, TV-

SPME with on-ber derivatization can serve

as a powerful technique for amine, GHB and

hydroxylamine-controlled substances [78]. The

technique can increase the efciency of the analyst

by minimizing the time required for preparation of

the sample for these types of analytes. Since GHB

cannot be analyzed directly in its native state by

GC/MS, this method is particularly well-suited to

overcome such limitation [72,79].

Fig. 4. Derivatization on-ber in TV-SPME

A review: Total vaporization solid-phase microextraction Yunes M. M. A. Alsayadi et al

Table 2. liquid injection methods based on V-SPME

Drug TV-SPME Liquid Injection

Methamphetamine + +

Amphetamine + +

Methamphetamine + TFAA + +

25I-NBOH 0 -

Gabapentin + +

Psilocin + +

25I-NBOH + TFAA + +

Pregabalin + -

Ephedrine + +

Ephedrine + TFAA 0 +

Lorazepam + +

Vigabatrin - -

GHB - -

Gabapentin + DMF-DMA 0 +

GHB + BSTFA + 1% TMCS + +

Vigabatrin + DMF-DMA - +

Pregabalin + DMF-DMA - 0

Fig.5. Immerged (graphene-Fe3SO4 –SPME Fiber) in water

and adsorbed the BTEX from water onto the ber

90 Anal. Methods Environ. Chem. J. 5 (3) (2022) 80-102

2.4. Application of TV-SPME procedure

2.4.1.Ascertainments of lipid proles of Phormia

regina

Pupae of Phormia regina was the sample used in

this study which basically belongs to a kind of blow

y species; while doing the inquiries of death, the

forensic entomologists commonly found this type.

which is commonly found by forensic entomologists

during the investigations of death. Conventionally,

the insect species analysis in a forensic backdrop has

been falling within the prospect of biologists along

with entomologists. Nevertheless, considerable

effect has been done by the chemistry domain for

the evaluation of these specimens by LC-MS, GC-

MS and likely analytical techniques [80]. Studies

that rely on liquid extraction are more commonly

used for such analysis. Usually, the pest is placed

in a non-polar solvent by the mean immersion for

a particular time, allowing the extraction process

of the cuticular and internal lipids. Derivatization

is a kind of needful for these excerpts to improve

performance and sensitivity within subsequent

separation steps [81-82]. Unavoidably, single or

multifold rounds of chromatography follows: liquid

chromatography (LC), gas chromatography (GC)

and thin layer chromatography (TLC) are some

of the techniques that have been used. This wide-

ranging method has been applied to the analysis of

pupae [83-86].

Some experiments have been sought for the evaluation

of the Volatile Organic Compounds (VOCs) that

emitted by pupae using HS-SPME at elevated

temperatures, unfortunately, the experiments were

unsuccessful. For that, attentions have been exerted

towards developing a new technique for the liquid

extraction of pupae in order for the isolation of any

hydrocarbons and lipids subsequent to TV-SPME

analysis. The derivatization by trimethlysilyl was

also performed internally within the sample vial

immediately before GC-MS analysis took place,

such derivatization would come very handy and

with potential advantage to future analysts in order

to rundown on blow y pupae [23].

A new-fangled technique has been developed

for the evaluation of sterols, fatty acids and

other naturally occurring lipids within pupae

of the blow y Phormia regina. Such method

counted on liquid extraction in a solvent (non-

polar), followed by derivatization using N,O-

bis(trimethylsilyl)triuoroacetamide (BSTFA)

w/ 1% trimethylchlorsilane (TMCS) carried out

inside the sample vial. The facilitation of this

rundown was done by total vaporization solid-

phase microextraction (TV-SPME), along with

gas chromatography-mass spectrometry (GC-MS)

which served as the instrumentation for analysis.

The TV-SPME delivery technique was considered to

be sensitive and effective approximately ve times

more than traditional liquid injection, this higher

sensitivity may ease the reconstitution requirement,

rotary evaporation, and collection of high-

performance liquid chromatography fractions, and

many of the other pre-concentration steps that are

commonplace in the current literature. In addition

to that, the ability of this method to derivatize the

liquid extract in just single step while ensuring

good sensitivity represents an improvement over

present derivatization method. Various saturated

and unsaturated fatty acids were the lipids present

by and large in y pupae, ranging from lauric

acid (12:0) to arachinoic acid (20:4), as well as

cholesterol. The concentrations of myristic acid

(14:0), palmitelaidic acid (16:2), and palmitoleic

acid (16:1) emerged as the most reliable indicators

of the age of the pupae [23, 87-88].

2.4.2.Detection of ɣ-butyrolactone (GBL) and

ɣ-hydroxybutyric acid (GHB) in alcoholic

beverages via TV-SPME and GC-MS

ɣ-butyrolactone (GBL) and ɣ-Hydroxybutyric

acid (GHB) are important drugs since the can

be spiked into a victim’s beverage to facilitate

sexual assault(surreptitiously). These drugs may

cause sedation, memory loss, and are difcult to

be detected especially in plasma and biological

samples. The challenge related to their analysis

of these drugs lies on that they may be prone to

readily interconvert in aqueous samples, which

was showed in samples that required longer time

to stand at room temperature. A volume required

A review: Total vaporization solid-phase microextraction Yunes M. M. A. Alsayadi et al

for the study of GBL in water was performed with

volumes that ranged from 1µl to 10mg as compared

to the efcacy of headspace SPME, immersion

SPME and TV-SPME. Lastly, water, liquor, wine

beer, and mixed drinks were spiked with either

GBL or GHB along with realistic concentrations

(mg/ml) and microliter quantities were analysed

using a combination of the TV-SPME and GC/

MS method. The volume study of GBL exhibited a

great sensitivity in the detection of GBL when TV-

SPME was used. In addition to that, GBL and GHB

were recognized in many beverages at realistic

concentrations. Overall, TV-SPME is a method of

benets since it does not require sample preparation

and uses lesser sample volume as compared to the

immersion and headspace SPME [73].

2.4.3.Detection of both cotinine and nicotine in

hair

TV-SPME can be used in detection of both cotinine

and nicotine in hair as biomarkers of tobacco users

whereas the cotinine detection was not possible

in the past by using conventional SPME [89].

Only few research papers have published in using

headspace SPME in the detection of nicotine

in human hair by using. It was reported for rst

time that both cotinine and nicotine are efciently

detected using TV-SPME from a hair sample

collected from a tobacco user. Incidentally, full

scan data detect many other important compounds

relied on a library search [53]. These involves

phenacetin (an analgesic), squalene (a hair lipid

that occurs naturally), 1,4-benzenediamine (a

precursor of hair dye), and homosalate (type UV

lter seen in shampoos). The hair taken from a

two more smokers had nicotine concentrations

of 21 and 29 ng mg-1 hair, which is almost same

as that the concentrations reported from other

studies [24,25]. A detailed studies of validating

the TV-SPME for the use of hair analysis showed

its ability to detect both the cotinine and nicotine

even in a small portion of the hair from the tobacco

users which could serve as a good method for

the researchers of toxicology and other medical

backgrounds [53].

2.4.4.Tracking explosive residues on the places

of bombing

The detection of the residues seen on bombing

places and that arising from a debris of post-blast has

a great role for the explosive’s investigators. This can

be used on the determining of explosive type, which

may be used to catch a link about some suspect. To

solve the issue of not nding a particle of explosives,

some standard methodology can be used including

the extraction of some pieces of debris with specic

solvent (i.e., acetone and/ or dichloromethane) and

then the extract(s) is to be analyzed via liquid injection

GC/MS and/or infrared spectroscopy [16,90]. A TV-

SPME method for the analysis of explosive residues

on pipe bomb fragments has been designed and

optimized. Optimization of this method was done

by the following parameters incubation temperature,

extraction time, and sample volume of the TV-SPME

method. For the nitroglycerin, method optimization

parameters were a 70 mL sample volume, a

30-minute extraction time and a 65 C incubation

temperature. In addition to that, TV-SPME showed

great sensitivity as compared to conventional liquid

extraction methods as it was found to be 13-fold more

sensitive and it has a very low detection limit (i.e.,

less than 10 ng mL-1). When this developed method

was used to actual pipe bombs, the recovery of the

estimated NG mean mass was 1.0 mg and the mean

concentration of NG on the fragments of steel was

almost 0.26 ppm (w/w). It was noticed that end caps

fragments yielded higher amount of NG and DPA.

These ndings could contribute to understand how

IEDs functioning and it help the analysts regarding

the required sensitivity for the analysis smokeless

powder from post-blast fragments.

Fragments from the end caps yielded the highest

amount of DPA and NG. These results of this study

contributed by the meaning of understanding of

how small IEDs function as well as inform analysts

regarding the sensitivity that is required for post-

blast analysis of smokeless powder. It is expected

that many other types of smokeless powder could

be analyzed by this technique. This technique also

can be used for the analysis of some other types of

containers like PVC [16].

92 Anal. Methods Environ. Chem. J. 5 (3) (2022) 80-102

2.4.5.Identication and Automated

Derivatization of Controlled Substances via

TV-SPME and Gas Chromatography/Mass

Spectrometry (GC/MS)

Due to polarity, many compounds that present in

biological and environmental samples are not suitable

to be analyzed by GC. In addition to that, some

compounds have the tendency to have decomposing

and adsorbing properties on the injector or columns

and to show non-reproducible peak areas, shapes

and heights [91]. To overcome such issues, the need

of introducing derivatization reactions arises [92].

The importance of derivatization comes from its

ability to decrease the polarity of the compounds

of interest and increase the volatility and improve

the analytes thermo stability. The derivatization

also can improve the process of selecting of

compounds behavior towards selective detectors,

such as the spectrometry (MS) and electron capture

detector (ECD). One of the main purposes from the

formation of derivatives is to enhance the selectivity

of the compounds, limit of detection (LOD) or

both [93]. Before applying the analytical method,

the targeted compounds placed for a procedure of

sample preparation that involves a derivatization,

concentration, or clean-up step procedures[26].

Combining extraction technique with derivatization

result in enhancing the separation characteristics,

detectability, and analyte recovery [94]. Generally,

derivatization has been performed to promote

the extractability of the analytes, reduce polarity,

improve the GC characteristics of compounds,

and make them compatible with the analytical

system and/or to increase the detection sensitivity

[91]. In forensic science laboratories, controlled

substances units are placed under pressure for

analyzing samples adapting methods that can show

cost-effectiveness and high throughput. Additional

to that, it is recommended in the eld of analytical

chemistry that that new chemical compounds

appear in forensic chemists and exhibits must

react to this by developing instrumental methods

have great selectivity and high specicity [95].

It was observed that TV-SPME offering greater

sensitivity for controlled substances as compared

to traditional liquid injection. Additionally, TV-

SPME technique was easily applied to involve

either a post-extraction or a pre-extraction on-ber

derivatization step species with thermally labile.

Promising results were obtained for almost all

categories of drugs that were analyzed successfully

by the meaning of on-ber derivatization as

solutions. This important discovery may increase

the use of this novel technique, because controlled

substances are existed mostly in their solid forms

in the laboratories of forensic science. This

technique can be applied in the determination of

solid drug powders and beverage sample, since

these applications include a signicant decrease

in the amount of sample preparation. Although not

applicable ideally for all analytes, TV-SPME with

on-ber derivatization could serve as an important

technique for the determination of hydroxylamine

and amine, controlled substances, and GHB. Thus,

this work results in a set of optimized derivatization

methods that can serve in TV-SPME and even in

liquid injection. This approach presents a possible

method for automated derivatization and sampling

for a wide variety of thermally labile compounds

and for analyzing compounds that need no

derivatization [72,74,96]. Many applications exist

for extraction analyte by the TV-SPME which was

shown in Figure 6.

2.4.6.VA-TV-SPME procedure

Considering that SPME is that method depended

on vaporizing the whole portion of the sample of

interest, including volatile, nonvolatile and semi-

volatile components. However semi-volatile and

non-volatile compounds needs more heat, for that

more amount of the sample volume is required. As a

resultant of that, the SPME ber get heated and that

ber has not affected the absorption of the analytes

on the SPME ber [53]. It could be a limiting factor,

and considered to be the main reason behind this

important extraction technique is not more used

widely. For that reason, publication studies based on

TV-SPME technique are less [23,69,70]. To solve

such limitations, TV-SPME is coupled with another

technique to encourage the analytes vaporization

A review: Total vaporization solid-phase microextraction Yunes M. M. A. Alsayadi et al

and the preparation steps are omitted lead to a great

reduction in the required heat which would assist

a great benet. In 2001, Brontun explained that

when there is inhibition of the vessel pressure, it

will lead to effect positively on the sampling [19].

One more explanation revealed that by decreasing

the pressure, the analytes gets released from the

matrix of the sample. Additional to that, decreased

pressure reduces the boundary layer that attached

to the ber and strengthens the analyte absorption

on the surface of the absorbent [49]. Recently, new

extraction technique was introduced by Psillakis

called Vac-HS-SPME as a new method depends

on reduction of the pressure of the vessel used for

sampling [76]. They revealed that when the vacuum

conditions are applied, HS-SPME the extraction

rate of analyte will be increased be speeding up

the conversion from the aqueous matrix to the

headspace. As a result of that, the vaporization

of the analytes increased attributed to vacuum

removal and faster equilibrium of the air from the

headspace. This technique could not be able to

extract analytes from the sample in solid phase and

soil without preparation [77]. The sample may be

lost due to the direct contact between the vacuum

and the sample while evacuation period occurring.

To overcome such risk, the need of using a novel

setup for the sampling vessel, Vacuum Assisted

HS-SPME (VA-HS-SPME) was introduced to

be used in the extraction of Polycyclic Aromatic

Hydrocarbons (PAHs) from polluted soil without

the need of preparation and the risk of analytes

loss is less [52]. In that proposed technique, for

the rst time, a low-cost, sample, reliable and fast

setup was developed by using both VA-HS-SPME

(low pressure) [78] and TV-SPME techniques.

One of the main advantages of VA-TV-SPME,

more temperature can be applied for the extraction

of analyte from the matrix of the sample without

increasing the ber temperature, which results

in the increasing the of analyte extraction, as

compare to conventional TV-SPME. One more

advantage is that the time of sample vaporization

is shorter. Also, when vacuum-assistance and

total vaporization are simultaneously used, it

maximizes the rate of analyte extraction in a

complex matrix, with no need of any preparation.

To evaluate the PAHs extraction from polluted

water samples, a PDMS ber is used, then the

determination is done by GC-FID [67]. The main

purpose of coupling TV-SPME with the VA-TV-

SPME system (Fig.7) was to increase the sensitivities

Fig. 6. Some applications of TV-SPME

94 Anal. Methods Environ. Chem. J. 5 (3) (2022) 80-102

in shorter times, which lead to lower extraction time

and temperature, as compared to the conventional

TV-SPME technique [67]. Such technique offers a

new method to solve the warm of the SPME ber

caused by the heating process needed for separating

the analyte from the matrix avoiding the use of

complicated equipment and the sample is vaporized

totally with lower duration as well as low heat energy.

Additional to that, the total vaporization of the sample

presents highly efciency due to the increasing of the

mass transfer in just one step. In addition to that, it is

possible to use of homemade and commercial SPME

ber, and there is potential for coupling with other

SPME techniques and automation, such as an inside

needle capillary adsorption trap (INCAT) or a needle

trap device (NTD [79].

2.5. Estimation of BTEX Compounds present

in Polluted water using GO-APTES Fiber and

Novel VA-TV-SPME Method

Isomers of benzene, toluene, ethylbenzene and

xylene, all together known as BTEX (Fig.8),

are highly volatile aromatic hydrocarbons and

considered to be among the most serious human

health and environmental risk issues.[32,97-98].

When these organic compounds are exposed

in higher concentrations, they cause a harmful

effects on central nervous systems, respiratory and

skin [89-100]. Leakage of oil pipelines may be

resulted by accidental fuel spills, and the disposal

contamination of oil companies efuents and

petrochemical, such pollutants have been released

into groundwater and other water sources [97].

As a result of that, many analytical methods were

developed such as a consequence, a wide variety

of analytical methods, such as narrow-bore tube

DLLME [38], ultrasound-assisted emulsication

microextraction [101] and in syringe dispersive

liquid–liquid microextraction (IS-DLLME). These

methods have been developed with motive of

extracting and determining of BTEX compounds

from water [102]. For the determination of BTEX

from contaminated water without using ant

additional steps for the extraction and the preparation

of the aqueous samples, microextraction techniques

were used. VA-SPME removed one of the most

partitioning steps in the conventional HS-SPME and

that can increase the speed and the sensitivity of the

method [102]. A novel and reliable microextraction

technique was used for the fast determination of

Fig. 7. Diagram of the VA-TV-SPME Assembly: in [A.] the cap of the sample is

caped in close system while in [B.] the cape of the system is opened

A review: Total vaporization solid-phase microextraction Yunes M. M. A. Alsayadi et al

benzene, toluene, ethylbenzene and xylenes (BTEX)

from contaminated water without any extra steps

for the preparation or extraction of the aqueous

sample. Vacuum-assisted-total vaporization-solid-

phase microextraction (SPME) eliminated one of the

partitioning steps in conventional headspace SPME

and caused an increase in the sensitivity and speed

of the method. A special nanocomposite SPME

bre made of grapheme oxide/3-aminopropyl-

triethoxysilane ber was utilize as the extraction

phase to attain an efcient extraction. Numerous

parameters were considered for the optimization,

the extraction time, temperature, and desorption

conditions. The optimized method exposed

acceptable a good validity aspects according to

the ICH guidelines with acceptable range. In this

study, BTEX that present in aqueous samples were

determined by the use of VA-TV-SPME method.

It was observed that effect of adsorption time is

less in the extraction efciency of VA-TV-SPME

[102]. Additional to that, in order to preconcentrate

and extract the analytes, an affordable and home-

made GO-APTES SPME ber was utilized and

it was observed that it has reliable and a powerful

sorbent, compared with that bres obtained from the

market commercially. For achieve a précised analyte

determination, this method was hyphenated with a

GC-FID instrument. According the outcomes of

this method, an analytical parameters such as LDR,

LOD and RSD were within the acceptable range,

and it was observed this method is suitable for the

determination of BTEX in polluted water[32,47,59].

3. Conclusion

The coupling TV with SPME arises from the need

for a technique where a complete vaporing of the

liquid samples gives a fewer matrix effect and better

adsorption. Such a method requires less sample

preparation, utilizes the least supplies, and can be

done automatically, enabling it to be both a cost-

effective and efcient method. TV-SPME is a sensitive

technique where the liquid aliquot is totality vaporized

prior to sampling, easing to attain the equilibria inside

the sample vial and increasing the quantity of analyte

available in the headspace. TV-SPME is an effective

technique for analyzing controlled substances with

and without on-ber derivatization. The approach of

coupling TV and SPME (TV-SPME) offered great

sensitivity and even low detection limits for compounds

present in the hair of tobacco users, such as nicotine

and cotinine. A sample extract needs to be heated until

it gets vaporized, and ber of SPME is utilized for pre-

concentrating analytes from the matrix.

4. Acknowledgement

The authors are heartily thankful to management of

Chandigarh University for constant encouragement,

support and motivation.

Fig. 8. Structures of BTEX

96 Anal. Methods Environ. Chem. J. 5 (3) (2022) 80-102

5. List of abbreviation

TV-SPME: Total Vaporization Solid Phase

microextraction

SPME: Solid Phase Microextraction

GC: Gas Chromatography

HS-SPME: Headspace Solid Phase Microextraction

MOF: Metal-Organic Framework

TATP: triacetone triperoxide

I-SPME: Immersion Solid Phase Microextraction

LC: Liquid Chromatography

IR: Infrared Spectroscopy

UV: Ultraviolet Spectroscopy

TV: Total Vaporization

PAHs: Polycyclic Aromatic Hydrocarbons

LVI: Large-Volume Injection

MS: Mass spectrometry

GC/MS: Gas Chromatography/ Mass Spectrometry

PDMS/DVB: Polydimethylsiloxane-divinylbenzene

LC-MS: Liquid Chromatography- Mass

Spectrometry

TLC: Thin Layer Chromatography

VOCs: Volatile Organic Compounds

BSTFA: Bis(trimethylsilyl)triuoroacetamide

TMCS: Trimethylchlorosilane

GLB: ɣ-butyrolactone

GHB: ɣ-hydroxybutyric acid

DPA: Diphenylamine

NG: Nitroglycerin

ECD: Electron Capture Detector

LOD: Limit of Detection

VA-TV-SPME: Vacuum Assisted Total Vaporization

Solid Phase Microextraction

VA-HS-SPME: Vacuum Assisted Headspace Solid

Phase Microextraction

PDMS: Polydimethylsiloxane

GC-FID: Gas Chromatography Flame Ionization

Detector

CAT: Capillary Adsorption Trap

INCAT: Inside Needle Capillary Adsorption Trap

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