Research Article, Issue 1

Analytical Methods in Environmental Chemistry Journal

Journal home page: www.amecj.com/ir

AMECJ

systems, atmospheric deposition is a significant

source of formaldehyde [1], and in drinking water

formaldehyde arises mainly from the oxidation

of natural organic matter during ozonation [2]

and degradation of oxygenates such as methyl

tert-buthyl ether (MTBE) and dimethyl carbonate

(DMC) [3]. It also enters drinking water via

leaching from polyacetal plastic fittings in which

the protective coating has been broken [4].

Formaldehyde is a very toxic compound and has

been classified as a human carcinogen by the

international agency for research on cancer (IARC),

and also as a probable human carcinogen by the

US. Environmental Protection Agency [5].The

Biochemistry Method: Simultaneous determination of formaldehyde

an d methyl tert-buthyl ether in water samples using static headspace

gas chromatography mass spectrometry

Ali Akbar Miran Beigia,*, Mojtaba Shamsipurb

a Oil Rening Research Division, Research Institute of Petroleum Industry (RIPI), Tehran, Iran

b Faculty of Chemistry, Razi University, Kermanshah, Iran

1. Introduction

Formaldehyde (HCHO) is the most widespread

carbonyl compound in the atmosphere. It enters

the environment from natural sources (including

forest fires) and from direct human sources such

as fuel combustion, industrial on-site uses, off

gassing from building materials and consumer

products. Although formaldehyde is a gas at

room temperature, it is readily soluble in water.

Formaldehyde is very active, and is transported

in air, water and contaminated soils. In aqueous

* Corresponding Author:A. A. Miran Beigi

E-mail: amiranbeigi@yahoo.com

https://doi.org/10.24200/amecj.v2.i01.40

:A R T I C L E I N F O

Received 5 Dec 2018

Revised form 30 Jan 2019

Accepted 15 Feb 2019

Available online 18 Mar 2019

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

Keywords:

Formaldehyde

MTBE

Static headspace-GC/MS

Oil refining

Wastewaters and Water

A B S T R A C T

The present study describes a method based on static

headspace extraction (HS) followed by gas chromatography/

mass spectrometry (GC/MS) for the qualitative and quantitative

analysis of methyl tert-buthyl ether (MTBE) and formaldehyde

(HCHO) in water samples. Cytochrome P4502A6 has important

role for converting of MTBE to tert-butyl alcohol (TBA) and

HCHO. To enhance the extraction capability of the HS, extraction

parameters such as extraction temperature, extraction time, the

ratio of headspace volume to sample volume and sodium chloride

concentration have been optimized. Wide linearity range was

verified in a range of 5-10000 µgL-1 for MTBE (r2=0.9998), while

those for HCHO was 5-500 µg L-1 (r2=0.9996). Detection limits

for MTBE and HCHO was 1.0 µg L-1 and 1.3 µg L-1, respectively.

Best results were obtained when the analyzed oily water samples

were heated to 70 ◦C for 20 min, with the sample volume 10

mL in 20 mL vial, and NaCl 30% (w/v) was used to saturate the

samples. The proposed analytical method was successfully

used for the quantification of analytes in water and wastewater

samples.

Determination of MTBE and HCHO in human; Ali Akbar Miran Beigi, et al

Analytical Methods in Environmental Chemistry Journal Vol 2 (2019) 33-42

34 Analytical Methods in Environmental Chemistry Journal; Vol. 2 (2019)

national institute for occupational safety and health

(NIOSH) considered formaldehyde as immediately

dangerous to life and health at 24 mgm-3 (20 µgmL-

1) [6]. It can damage the person’s nerve system, lung

and liver, and cause irritation of eyes, nose, throat

and skin. Therefore, formaldehyde is one of the

analytical interesting substances as a marker of fuel

additive degradation. Its determination becomes

also a hot spot of the research especially in oily

wastewater matrices. A variety of methods for the

determination of formaldehyde have been reported,

including spectrophotometry [7-13], flow-injection

catalytic method [14], high performance liquid

chromatography [15], gas chromatography [16,

17], isotope dilution mass spectrometry [18],

fluorimetry [19, 20], chemiluminescence [21,22],

polarography [23], Fourier Transform Infrared

Absorption [24] and sensors [25-28]. MTBE is also

a volatile organic compound (VOC) produced from

natural gas. It is primarily used for the oxygenation

of fuel to enhance octane number and to improve

the combustion process, in order to reduce

carbon monoxide emissions [29]. MTBE readily

dissolves in water, and moves rapidly through

soils and aquifers. It is resistant to microbial

decomposition and difficult to remove in water

treatment. Its occurrence in the environment is of

a great concern because of the toxicity of MTBE

and its degradation products [30]. Since MTBE is

highly volatile and very soluble in water, it can be

easily found both as airborne pollutants of living

and working environments and as contaminants

of drinking water [31]. To date limited data are

available on the effects of MTBE on health.

Notwithstanding this, USEPA has concluded that at

high doses, MTBE is a potential human carcinogen

and recommended that MTBE levels in drinking

water be kept below a range of 20-40 ppb [32].

MTBE and other oxygenates in ground waters

are frequently measured using standard US EPA

approved methods (e.g., EPA 8021B, EPA 8260B,

ASTM D 4815). These procedures usually perform

gas chromatographic separation coupled with

photo ionization detector (PID), flame ionization

detector (FID) or mass detector (MS). The

introduction of analytes in the chromatographic

apparatus is performed either via direct injection

of water samples (DAI) [33,34], or using sampling

techniques as dynamic headspace (P&T), static

headspace [35], solid phase microextraction

(SPME) [36-44], and solvent microextraction

(SME) [45,46]. The DAI technique presents some

difficulties to be coupled with capillary GC, due to

the large expansion volume of water. Direct water

injections are prone to back flush in the injector

port, which can cause loss of analyte response

as well as injection port contamination. MTBE

oxidation can generate tert-buthyl alcohol (TBA)

and formaldehyde (Fig.1). Our previous study

demonstrated that human cytochrome P450 2A6

is able to metabolize MTBE to tert-butyl alcohol

(TBA) and formaldehyde, a major circulating

metabolite and markers for exposure to MTBE [3].

CYP2A6 plays a significant role in metabolism of

gasoline ethers in liver tissue. The purpose of this

present study is to develop a simple, sensitive and

selective method for simultaneous determination

of trace amounts of formaldehyde and MTBE in

environmental and water matrices. To our

knowledge, no method was found in the literature

for this case.

2. Experimental

2.1. Chemicals and Standard Solutions

In this work, analytical grade of chemicals and

reagents were purchased from Merck, Germany.

3HC

CH3

COCH3 3HC C OH

CH3

HCHO

MTBE

Formaldehde

TBA

Fig. 1. MTBE oxidation reaction

Determination of MTBE and HCHO in water Ali Akbar Miran Beigi, et al

with a heatable CTC agitator for incubation and

shaking, and a robotic arm. To prevent the carry over

of analytes, we used a heated ﬂushing station for

conditioning of the HS needle and reconditioning

after each analysis. Both the gas station and the

heated ﬂushing station were ﬂushed with nitrogen.

The syringe body was held in the syringe adapter

heater. 20 mL vials sealed with screw top caps

with PTFE/silicon septa were used. Parameters of

the instrument are shown in Table 1. A salt content

of 30 (% w/v) was chosen for the quantitative

determination of target analytes in

environmental and water samples.

The GC–MS analysis was performed using a Varian

(CP-3800 series) gas chromatograph equipped

with a mass-selective detector (Varian, quadrupole

1200) and a factor-four, VF-5ms fused-silica

capillary column with a 30m × 0.25 mm i.d. and

250 um ﬁlm thickness (Varian) was used. The GC

conditions were as follows: inlet temperature, 250

◦C; inlet mode, split operation with split ratio 1:25.

The oven temperature was set at 50 ◦C and raised to

100 ◦C at 5◦C/per min, and raised to 275 ◦C at 20 ◦C

per minute. The ﬁnal temperature was maintained

for 1.75 min and the total run time was 20 min.

Helium, at a constant ﬂow rate of 1.5 ml/min was

used as the carrier gas. Mass spectra were obtained

at 70eV in the electron impact ionization mode; the

spectrometer was operated in the full scan mode

over the mass range from 75 to 110(m/z). The

source, transfer line and quadrupole temperatures

were maintained at 200◦C, 250 ◦C and 200 ◦C,

respectively. Total ion current chromatograms were

acquired and processed using Workstation data

analysis software (Varian). To increase sensitivity,

the selected ion monitoring (SIM) mode was

applied in quantitative analysis. The most abundant

ion was used as the quantified ion. In Table 2, some

Double distilled water (DDW) was used for

preparation and dilution of samples. Helium and

nitrogen (ultrapure carrier grade) were obtained

from Roham gas Company (Tehran, Iran). An

aqueous formaldehyde stock solution, 1000 gm

L−1, was prepared by diluting 2.5mL of 37%

w/v stock formaldehyde solution (Merck) to 1 L

with deionized distilled water (DDW) and was

standardized by the sulfite method [47]. Working

solutions of formaldehyde were subsequently

prepared by appropriate dilution of the stock

solution with DDW. MTBE Calibration stock

solutions were prepared by adding 10 µL of pure

MTBE (99.5%, Merck) to 10 ml of MeOH (Merck)

in a 10ml vial with a PTFE-silicon septum. The

mixture was manually agitated for 5 min. The

first dilution steps were performed with methanol

whereas further preparation of the standard

solutions was carried out with DDW. The standard

solutions used within 4 weeks. All sample and

standard vials were completely filled to eliminate

headspace. Individual and cumulative working

standard solutions were obtained by appropriate

dilution of the stock in 50 ml of methanol and

further diluted in ultrapure Milli-Q water to prepare

solutions containing MTBE and formaldehyde at

the nanogram per milliliter level. The method was

optimized with MTBE and formaldehyde solutions

of 50 µg/L-1 concentration. It should be noted that in

this work Methyl ethyl ketone (MEK) (50 ng mL-1)

was used as internal standard in environmental

and water samples.

2.2. Apparatus and Procedure

Static headspace analysis was performed using

a CTC-CombiPAL autosampler (Bender and

Holbein, Zurich, Switzerland) mounted on top of

a GC-MS system. The autosampler was equipped

Table 1. Headspace conditions

Plunger fill speed: 100 µLper secSyringe Temperature : 71ºC

Pre-injection delay: 4 secAgitator Temperature : 70ºC

Plunger injection speed:250 µLper secSample incubation time: 20 min

Syringe flush time:120 secAgitator speed: 500 rpm

sample volume, 10 ml in 22 ml vialAgitation cycle: 2 sec on, 4 sec off

Analytical Methods in Environmental Chemistry Journal; Vol. 2 (2019)

analytical conditions of MTBE, formaldehyde and

methyl ethyl keton by GC-MS with SIM mode

are shown. All quantiﬁcations made in this study

were based on the relative peak area of analytes

to the internal standard from the average of three

replicate measurements in environmental and

water samples.

3. Results and discussion

Various parameters were evaluated during the

method development. In the present study, the

evaluation of individual parameters was carried

out while all other method parameters were kept

constant.

3.1. Extraction temperature

The temperature of sample affects on evaporation

of analyte into the headspace. We expected that

an increase in sample temperature will result in

improved the extraction efﬁciency, because of the

increased evaporation of the analyte concentration

in the headspace. The effect of sample temperature

was studied by changing the sample temperature

from 40 to 80 ◦C. As can be seen in figure 2, the

amount of extracted analyte (into the headspace)

increases with increasing temperature up to 80 ◦C.

In headspace analysis, it is recommended not to

use high temperatures (in order to avoid the over-

pressurization of the vial sample, and so avoid

accidents) and, therefore, an extraction

temperature of 70◦C was selected in environmental

and water samples. The syringe temperature of

5◦C above vial temperature was selected to avoid

the analytes condensation.

3.2. Extraction time

The time required for the extraction process was

an important parameter to be investigated. The

most adequate time for the HS extraction was

considered to be the time reaching the equilibrium

of the analytes between the vapor phase and

aqueous phase. Extraction time between 5 and 30

min were tested for the samples of 50 µg L-1 at

70°C, and the heating-time proﬁle for the MTBE

and formaldehyde mixture is shown in figure 3.

An increasing efficiency was observed for both

Table 2. Analytical conditions of MTBE, formaldehyde and methyl ethyl ketone by GC-MS with SIM

Quantification ions (m/z)Retention time (min)Molecular weightCompound

301.3930

Formaldehyde

731.4588MTBE

431.9073Methyl ethyl keton

Fig. 2. Influence of the extraction temperature on

the relative peak areas of 50 µgL-1 MTBE and

formaldehyde in water.

1750

1770

1790

1810

1830

1850

1870

1890

10000

20000

30000

40000

50000

60000

70000

80000

90000

020 40 60 80 100

Peak area (×1000 counts)

Peak area (counts)

Temperature (oC)

MTBE

HCHO

Fig. 3. Effect of extraction time on peak areas of 50

µgL-1 MTBE and formaldehyde in water at 70 oC.

5000

10000

15000

20000

25000

30000

35000

40000

45000

50000

010 20 30 40

Time (min)

Peak area (counts)

830000

850000

870000

890000

910000

930000

950000

970000

Peak area (counts)

HCHO

MTBE

M TBE

HCHO

Determination of MTBE and HCHO in water Ali Akbar Miran Beigi, et al

compounds when the longer extraction time

was used until 20 min, and then an increase in

extraction time caused a decrease in the efficiency.

A reason for this phenomenon was the transfer of

water molecules to headspace which diluted the gas

phase and decreased extraction amounts. So the

extraction time of 20 min was considered for the

subsequent experiments.

3.3. Ionic strength inﬂuence

Because the ionic strength of the solution

influences the partition coefficient between the

gas and liquid phase (K) the effect of salt amount

on extraction efficiency was also checked. The

effect of the salt on the extraction efficiency was

investigated by comparing the extraction efficiency

of samples which contained different amounts of

sodium chloride (NaCl) from 0 to 40 (%w/v), and

its influence, as the salting out agent, on the ion

abundance of GC-MS chromatogram for MTBE

and formaldehyde is shown in figure 4. As can be

seen the addition of salt does not have the same

effect for both target analytes: the addition of NaCl

led to better results in the case of MTBE, while for

the HCHO no favorable, and sometimes unfavorable

effects (when more than 30% (w/v) of sodium

chloride were employed ) were observed. In human

blood, the effect of different ions on extraction

of Formaldehyde and MTBE based on proposed

procedure was investigated. The interference of

some coexisting ions in blood, serum and urine

samples on the recovery of Formaldehyde and

MTBE was studied under optimized condition. The

proposed procedure was performed using a 10 mL

sample containing 5-500 µgL-1 of formaldehyde

and MTBE and 2 mg L-1 of different concentration

of matrix ions such as, Zn2+, Cu2+, Mn2, Na+, K+,

Ca2+ and Mg2+. The tolerate amounts of important

ions and biological matrix (albumin and proteins)

were tested that caused less than 6% of the head

space extraction alteration. In optimized conditions,

the ions and biological matrix do not interfere to

formaldehyde and MTBE extraction by procedure

(less than 5%). The results showed us, the most of

the probable water matrix concomitant have no

100000

200000

300000

400000

500000

600000

700000

800000

900000

010 20 30 40 50

NaCl content (w/v%)

Peak area (counts)

30000

35000

40000

45000

50000

55000

60000

65000

70000

Peak area (counts)

HCHO

MTBE

M TBE

HCHO

Fig. 4. Effect of NaCl additives on detector

response areas of 50 µgL-1 MTBE and formaldehyde

in water produced by HS for 20 min at 705 oC and

sample volume 10 mL in 20 mL vial

considerable effect on the recovery efficiencies of

formaldehyde and MTBE.

For MTBE the headspace extraction efﬁciency is

increased with increasing concentration of salt in

environmental samples and it reached the peak

yield when NaCl (30%, w/v) was used to saturate

the samples. The reason was considered to be the

increase of ionic strength in aqueous samples by

adding salt, therefore the solubility of analytes

was decreased and more analyte was released into

the headspace. For HCHO the observed behavior

could be explained on account of its high solubility

in water (37%) and strong interaction by solvent

molecules (water) through hydrogen bonding

that cause a greater affinity for water samples.

Therefore, 30 % (w/v) salt content was chosen

for the quantitative simultaneous determination of

both target analytes.

3.4. Sample volume

The ratio of sample volume to headspace volume

is an important parameter that affects the extraction

efficiency of HS. An increase in sample volume and,

consequently, a decrease in headspace volume enhance

the extracted amount of analyte, which improves the

sensitivity. The optimal ratio of the aqueous volume

to the headspace volume for headspace analysis in

20 mL vials was determined by varying the sample

38 Analytical Methods in Environmental Chemistry Journal; Vol. 2 (2019)

volume from 5 mL (1/4 vial volume ) to 15 mL

(3/4 vial volume ). The results are also shown in

Figure 5. The extracted amounts of analytes increase

continuously with increasing sample volume reach a

maximum at an aqueous volume of 10 ml and then

decrease because of the decreased volume of the

headspace. In the work, sample volume of 10.0 mL

(in 20.0 mL vial) was used.

3.5. Evaluation of the method performance

Figure 6 shows a typical total ion chromatogram

(TIC) of a standard solution containing, 100 µg

L-1 of MTBE and HCHO after its headspace

extraction under optimal experimental conditions

in water/wastewater and environmental samples.

The linearity, limits of detection and precision

were calculated when the optimum conditions for

the HS-GC–MS procedure were established. The

linearity of the method was examined by spiking

DDW with MTBE and HCHO in a concentration

range from 5 to 10000 µg L-1 in water samples

and 5 to 500 µg L-1 in waste biological samples.

Each solution was submitted to the HS-GC-MS

analysis three times. The Figures of merit of the

calibration graphs are summarized in Table 3. A

plot of the peak areas against the concentrations of

standards was obtained (Fig.7). Lack-of fit test was

performed to check the goodness of fit and linearity

[48]. Lack-of-fit test demonstrated that the linear

models were adequate because the whole p values

were more than 0.05 at significance level of 95%.

(Table 4).The linear range experiments provided

the necessary information to estimate LODs, based

on the signal that differed three times from the

blank average signal, was 2 and 5 µg L-1 for MTBE

and HCHO, respectively. Analytical accuracy was

assessed from the recovery of analyte spiked to

various of water and environmental samples

(Table5). The repeatability expressed as the

relative standard deviation (R.S.D.) was

obtained by carrying out five replicate assays on

each water samples (Table 2), and gave a value

less than 4.8% and 2.6% in water and

environmental samples, respectively. Therefore,

this method is deemed acceptable for determining

of trace level of µg L-1 in water and

wastewater matrix.

Fig. 6. Total ion chromatogram (TIC) in SIM mode

of an ultrapure water solution contaminated with

MTBE (50 µgL-1) and formaldehyde (50 µgL-1),

extracted using static headspace. Extraction conditions:

Extraction time: 20 min, Extraction temperature: 70

oC, sample volume 10 mL in 20 mL vial and NaCl

30% (w/v).

10000

20000

30000

40000

50000

60000

0 5 10 15 20

Volume (mL)

Peak area (counts)

745000

750000

755000

760000

765000

770000

775000

780000

Peak area (counts)

MTBE

HCHO

M TBE

Fig. 5. Effect of solution volume in 20 ml vial on

peak areas of 50 µgL-1 MTBE and formaldehyde in

water produced by HS for 20 min at 70 oC.

Determination of MTBE and HCHO in water Ali Akbar Miran Beigi, et al

Samples 2 and 3 are also the same

synthetic sample 1 that are treated by 20

picomol of human cytochrome P450 (2A6),

prepared from Sigma-Aldrich Co., at 37 oC

for 13 and 30 minutes, respectively.

Cytochrome P450 (2A6) is known as one of the

most effective enzymes in metabolism

alkoxyethers. In order to control enzyme

activity and termination of reaction time, it was

need to a deactivator such as 100 µL of 0.10 M

perchloric acid. Formaldehyde was also a mainly

byproduct of enzymatic degradation reaction of

MTBE and was detected by developed method as

given in Table 6. In the case of formaldehyde,

although the calculated values can be estimated

stoichiometrically.

Fig. 7. Standard calibration curves of peak areas against the concentrations of MTBE () and HCHO (). MTBE: y

= 14.90x + 28.32 (r = 0.996), HCHO: y = 61.07x + 88.88 (r = 0.998).

Table 3. Analytical figures of merit of the determination of MTBE and HCHO (µg L-1)

Compound Regression Equation aLinear Range LOD

RSD

(%, n = 5)

0.1 40

MTBE y =513.24x+0.319 5-10000 2 4.8 6.8

formaldehyde y = 1.759x + 27.53 5-500 5 1.9 7.8

a y: analyte area-to-internal standard area, x: concentration (µg

L-1).

3.6.Analysis

The proposed method was firstly used to

quantify MTBE and HCHO in water and

wastewater of Tehran oil refinery. The obtained

results in Table 5, showed good recoveries, and the

method was ideally suited for these matrices. The

synthetic biological samples were also

analyzed by the develop method (Table 6).

Here, blank is containing 500 µL mixture of 50

mM tris-HCl buffer (pH=7.4), 1mM NADPH (as

inducer), 10 mM MgCl2 and 150 mM KCl (as

electrolytes). Synthetic sample 1 is prepared by

addition of 5.02 µg ml-1 MTBE in the blank

solution.

Table 4. Evaluation of the goodness of ﬁt and linearity of calibration graphs

Compound Correlation coefﬁcient, r Determination coefﬁcient, R2Lack-of-fit, pa

MTBE 0.9998 0.9993 0.089 > 0.05

Formaldehyde 0.9996 0.9984 0.078 > 0.05

a Confidence interval, 95%.

Analytical Methods in Environmental Chemistry Journal; Vol. 2 (2019)

5. References

[1] R.J. Kieber, M.F. Rhines, J.D. Willey, Rainwater

formaldehyde: concentration, deposition and

photochemical formation, Atmos. Environ., 33 (1999)

3659-3667.

[2] J. K. Fawell, Formaldehyde in Drinking-water,

Background document for development of Guidelines

for drinking-water quality, World Health Organization

(WHO), UK, 2005.

[3] M. Shamsipur, A. A. Miran Beigi, M. Teymouri,

T. Poursaberi, S.M. Mostafavi, P. Soleimani,

Biotransformation of methyl tert-butyl ether by

human cytochrome P450 2A6, Biodegradation, 23

(2012) 311-318.

[4] R.G. Liteplo, R. Beauchamp, M. E. Meek, R. Chenier,

Concise international chemical assessment document

40: formaldehyde, World Health Organization

(WHO), Geneva, 2018.

[5] U.S. Environmental Protection Agency (USEPA),

report to congress on indoor air quality, assessment

and control of indoor air pollution, Volume 2, 2017.

[6] National Institute for Occupational Safety and Health

(NIOSH), Manual of analytical methods, 4th ed.,

department of health and human services, Cincinnati,

OH, USA, 2018.

[7] G. Nael, Y. H. S. Maha, A. Mosallb, Spectrophotometric

determination of formaldehyde based on the

telomerization reaction of tryptamine, Arabian J.

Table 5. Determination of HCHO and MTBE in water and Human samples at optimum extraction conditions (µg L-1)

Well water c

Tap water

Water Recovery (%)Found

aAddedConc.Recovery (%)Found

aAddedConc.

95.623.9 ± 4.225.0NDb

100.825.2 ± 2.825.0NDb

HCHO

97.036.2 ± 3.125.012.097.624.4 ± 4.825.0NDb

MTBE

PetrochemicalOil company

Wastewater Recovery (%)Found

aAddedConc.Recovery (%)Found

aAddedConc.

97.022.5 ± 4.210.012.896.541.4 ± 2.320.022.1HCHO

96.019.3 ± 3.110.09.7103.136.9 ± 1.520.016.3MTBE

a Mean of triplicates with percent R.S.D (n=5).

b Not found.

c Well water nearby Tehran oil refinery.

The standard method based on derivatization

with 2, 4-dinitrophenylhydrazine and HPLC

detection was used to assay the values[49]. An

average recovery of 65.5 and 91.7 % was obtained

for degradation process of MTBE after passing 13

and 30 min from course of the reaction,

respectively. The SD of measurements at ppm

levels was not greater than 2.6%.

4. Conclusions

An automated and simple method has been

developed for simultaneous determination of MTBE

and formaldehyde in water and human matrices.

It was based on the use of HS device coupled

with a GC–MS instrument. The no necessity of

consumables or reagents for sample treatment made

HS-GC–MS to be considered as the best extraction

option of the studied ones. The analysis required

20 min of sample incubation or extraction time and

less than 5 min for chromatographic determination

programming the MS detector in SIM acquisition

mode. Good precision and the simple sample

preparation enable to use this procedure for

routine investigations. This proposed method was

then applied to the analysis of human biological

and environmental samples (synthetic biological

samples).

Table 6. Simultaneous determination of MTBE and Formaldehyde in synthetic biological samples

Formaldehyde / µgml-1

MTBE / µg ml-1

SampleNo.

FoundCalcd.FoundCalcd.

--4.915.02Synthetic sample 11

1.141.091.73-Synthetic sample 22

1.531.480.415-Synthetic sample 33

Determination of MTBE and HCHO in water; Ali Akbar Miran Beigi, et al

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