Research Article, Issue 4
Analytical Methods in Environmental Chemistry Journal
Journal home page: www.amecj.com/ir
AMECJ
------------------------
1. Introduction
Heavy metal is important factor must be controlled
in environmental air and patients. There are some
heavy metals with toxic effects such as mercury,
cadmium, nickel, vanadium, arsenic, lead and
aluminum which have no known beneficial effect
on organisms. Mercury has been documented to
cause autoimmune and neurological diseases.
Mercury simply vaporizes at room temperature
and easily enters to the environment and human
lungs. High concentration of mercury vapors in
work place air can accumulate in human tissues
as compared to non- occupationally exposed
individuals. Adverse health effects of this exposure
including subtle neurological side-effects have
also been well documented in most Petrochemical
workers even at the lowest levels of exposure;
consequently, measurement of mercury and methyl
mercury in blood, urine, hair and air briefing seems
to be important [1-7]. Chlor-alkali workers are
mostly exposed through breathing air of mercury
vapors which was released from electrochemical
system to human body such as lungs and skin.
Corresponding Author: Ali Ebrahimi *
E-mail: Ali.Ebrahimi.ohe@gmail.com
https://doi.org/10.24200/th amecj.v2.i04.81
Seyed Mojtaba Mostafavi a and Ali Ebrahimi b,*
a Department of Chemistry, Iranian-Australian Community of Science, Hobart, Tasmania, Australia
b Occupational Health Engineering Department, School of Public Health, Qom University of Medical Sciences, Qom, Iran
Mercury determination in work place air and human biological
samples based on dispersive liquid-liquid micro-extraction
coupled with cold vapor atomic absorption spectrometry
A R T I C L E I N F O:
Received 13 Sep 2019
Revised from 18 Nov 2019
Accepted 11 Dec 2019
Available online 28 Dec 2019
Keywords:
Mercury,
Analysis,
Dispersive liquid-liquid micro-
extraction,
Human blood,
Work place air
A B S T R A C T
Mercury as a toxic heavy metal is important factor must be determined
and controlled in work place air and human biological samples. It should
be mentioned that, mercury (Hg) get distinguished from other toxic
environment pollutants, due to their non-biodegradability which accumulate
in living tissues of human body. By NIOSH method, the briefing work place
air of worker was measured by flow injection cold vapor atomic absorption
spectrometry (FI-CV-AAS). For separation and preconcentration mercury
from blood/urine samples, a new procedure based on benzyl 1H-pyrrole-
1-carbodithioate (BPDC; C12H11NS2) was used by ultrasonic liquid-liquid
micro-extraction (ULLME) coupled with cold vapor atomic absorption
spectroscopy (CV-AAS). The influences of various analytical parameters
including pH, BPDC concentration, sample volume and ionic liquid volume
were investigated. The quantitative recoveries and enrichment factor were
obtained more than 95% and 9.8, respectively at pH=7. The detection of limit
(LOD) and detection of quantification (LOQ) of mercury were 30 ng L-1 and
0.1 μg L-1 respectively. In order to calculate the validation and accuracy of
proposed method, the certified reference materials (NIST, CRM 3133 Lot
061204) was used and analyzed by ULLME-CVAAS. So, proposed method
had good potential for preparation and preconcentration mercury in human
blood / urine samples of worker and workplace air before analysis.
Analysis in occupational health Ali Ebrahimi et al
Analytical Methods in Environmental Chemistry Journal Vol 2 (2019) 49-58
50 Analytical Methods in Environmental Chemistry Journal; Vol. 2 (2019)
Family members of these workers may also become
exposed to mercury through personnel’s clothes
contaminated with mercury particles. Ingested
metallic mercury enters the body through the
stomach or intestines but even in large amounts very
little enters the body. On the other hand, breathing
mercury vapors results in direct absorption of
most it (about 80%) from the lungs which rapidly
moved to other organs, including the brain and
kidneys. Mercury get distinguished from other
toxic pollutants due to their non-biodegradability
can accumulate in living tissues of human body.
Even a very small amount of them can cause severe
physiological or neurological damage to the human
body [8-14]. The concentration of mercury vapor
in air reported by occupational safety and health
administration guidelines (OSHA, 0.1 mg m-3).
In addition, national institute for occupational
safety and health (NIOSH) has established a
recommended exposure limit for mercury vapor
of 0.05 mg m-3 for up to an 8-hour workday and
a 40-hour workweek. American conference of
governmental industrial hygienists (ACGIH) has
assigned mercury vapor a threshold limit value of
0.025 mg m-3 for a normal eight-hour workday and
a 40-hour work week .Mercury levels in blood can
be used to help diagnose recent mercury exposure
and to evaluate patient response to chelation
therapy. Normal mercury concentration in human
blood/urine is less than 10-20 μg L-1 [15-19]. Many
analytical methods such as atomic fluorescence
spectrometry [20-24] high-performance liquid
chromatography [25] Gas-chromatographic [26]
plasma mass spectrometry [27] high-performance
liquid chromatography on-line coupled with
cold-vapor atomic fluorescence spectrometry
[28, 29] gas chromatography-mass spectrometry
[30] ion chromatography using photo-induced
chemical vapor generation atomic fluorescence
spectrometric detection [31] ion chromatography
coupled with ICP-MS [32] liquid chromatography
hyphenated to cold vapor atomic fluorescence
spectrometry [33] UV–Vis spectrophotometric
[34] were used for mercury spices determination.
Samples preparation and preconcentration before
analysis is an important factor for determination
of pollutants in different matrixes. Recently,
the various methods for the preparation and
preconcentration of mercury compounds, including
solid phase extraction (SPE) [35-43], gold trap
[44], ionic liquid-based dispersive liquid-liquid
microextraction (IL-DLLME) [45, 46], cloud
point extraction (CPE) [47,48], electromembrane
extraction [34], dispersive solid phase micro-
extraction [49], single-drop microextraction [50],
and Liquid–liquid extraction (LLE) [51], were
reported. Since 2010, the DLLME method has
been used for extraction and/or preconcentration of
different analytes from aqueous samples [52, 53].
By DLLME method, extraction solvent such as ionic
liquids, liquid phase (sample) and disperser solvent
(acetone) was used [54]. The DLLME procedure
has many advantages including simple, rapid, low
time and cost, and efficient extraction. The green
analysis such as, decrease solvent volume and less
waste generation due to preparation and analysis
samples was achieved [53-54]. In this study, the
mercury concentration in human blood and urine
samples based on BPDC –IL was determined by
FI-CVAAS after ULLME procedure in 50 samples.
In addition, 50 briefing air based on Hopcalite was
analyzed by NIOSH method (6009).
2. Experimental
2.1. Apparatus
The experiments were performed using the flow
injection cold vapor atomic absorption spectrometer
(FI-CVAAS, GBC – 932, 3000, Australia). All
containers (quartz crucibles, plastic tubes) were
cleaned with detergent and treated successively by
the hydrochloric acid and rinsed with de-ionized
water. Microwave digestions were carried out with
a multi-wave 3000 (Anton Paar, 100 mL, 20 bars;
Austria). The pure argon gas (99.99%) was used
as a carrier gas for CV-AAS analysis and the pH
values of the solutions were measured by a digital
pH meter (Metrohm 744). Personal sampling pump,
Sampler (glass tube, 7 cm long, 6-mm OD, 4 mm
ID, flame sealed ends with plastic caps containing
one section of 200 mg Hopcalite held in place by
51
Analysis in occupational health Ali Ebrahimi et al
glass wool plugs (SKC, Inc., Cat. Num. 226-17-
1A, or equivalent) and BOD bottle were used for
collection of air and blood/urine in the industrial
factory respectively.
2.2. Reagents and Materials
All chemicals of analytical reagent grade such as
nitric acid, hydrochloric acid, benzyl 1H-pyrrole-1-
carbodithioate (BPDC; C12H11NS2) (CAS no 60795-
38-2), Polyoxyethylene octyl phenyl ether (TX-
100), and sodium borohydride (NaBH4) were from
Merck Germany. Mercury standard solutions were
prepared from a stock solution of 1000 mg L-1 in 1%
nitric acid from Fluka Switzerland. Reducing agents
(aqueous solution of 0.6% sodium borohydride in
0.5% sodium hydroxide) were prepared freshly
and filtered before use. Ionic liquid (1-butyl-3-
methylimidazolium hexafluorophosphate; [BMIM]
[PF6]; C8H15F6N2P) (1-Ethyl-3-methylimidazolium
hexafluorophosphate ;[EMIM][PF6]; C6H11F6N2P )
(Trimethyl imidazolium hexafluorophosphate ;
[DMMIm][PF6]) was purchased from Sigma
Aldrich. Buffer solutions were prepared from 2-1
mol L−1 sodium acetate and acetic acid for pH=
3-7. Ultrapure water was prepared from Millipore
(Germany).
2.3. Sampling
For sampling, all glass tubes (sampling vessel)
were washed with a 1 moL L-1 HNO3/HCl solution
for at least 24 h and rinsed 10 times with DW before
using. Due to low mercury concentrations in whole
blood/urine, even minor contamination at any
stage of sampling, sample storage and handling, or
analysis has the potential to effect on the accuracy
of the results. 10 mL blood and 100 mL urine
samples were collected from factory workers and
healthy matched controls (20-55 years), living in
Abadan (IRAN). For analysis of 45 blood samples,
5 microliter of heparin (free metals) was added.
The human blood and urine sample was maintained
at –20 °C in a cleaned glass tube.
45 air samples were collected in an employee’s
breathing zone according to 6009 NIOSH
analytical method. Each personal sampling pump
was calibrated with a representative sampler and
the end of sampler was broken immediately prior
to sampling. Samplers were attached to the pumps
with flexible tubing and air was collected at a rate
of 200 to 300 mL min-1.
2.4. General procedure
In this research, human blood and urine and
briefing air samples of factory workers were
studied. The determination of mercury in blood/
urine and air was carried out using a flow injection
cold vapor atomic absorption spectrometry
system after sample treatment according to the
ULLME procedure. Based on procedure, the
BPDC as complexing agent was added to human
samples and mercury extracted by ULLME as
a new mode of liquid phase extraction with high
recovery and extraction efficiency. In this work,
0.5 mL of 2% (w/v) BPDC solution was prepared
and added to 10 mL of blood and urine samples
and pH was adjusted to 7 with buffer solution in
a centrifuge tube. Then, 0.2 g of different IL was
added to the mixtures and they were shaken with
a vortex apparatus for 5 min. Mercury (HgII) was
complexed and pre-concentrated as Hg-BPDC-IL
([BMIM][PF6]). The phases were separated by
centrifuging of turbid solution at 4 min with 3500
rpm. After separation of ionic liquid from liquid
phase, the remained solution (Hg-BPDC-IL) was
back extracted with nitric acid (0.5 M, 0.5 mL) and
the mercury concentration in blood/urine samples
was determined by FI-CV-AAS (Fig 1).
Air samplers were capped and pack securely
for shipment. Based on NIOSH procedure, the
Hopcalite sorbent and the front glass wool plug
from each sampler were placed in separate 50-ml
volumetric flasks and mixture of 2.5 mL of HNO3/
HCl concentration added to volumetric flasks.
Hopcalite sorbent was dissolved in acids and
diluted to 50 mL of deionized water (blue color),
then the mercury concentration was determined
with FI-CV-AAS.
3. Results and Discussion
Analytical conditions for mercury determination
52 Analytical Methods in Environmental Chemistry Journal; Vol. 2 (2019)
were performed in briefing air and human blood
and urine samples of chemical factory workers at
this work. Absorption (S/N) and repeatability of
the results were investigated for the determination
mercury by FI-CVAAS. The instrumental and
extraction conditions are listed in Table 1. Working
range was between 0.05- 7.1 μg L−1 for samples at
peak area.
The complexation phenomenon is strongly
conditioned by the pH. The results showed us the
pH from 5.5 to 7.5 was good recovery for mercury
extraction by BPDC. So pH=7 selected as favorite
pH for further analysis in blood samples (Fig 2).
The minimum BPDC concentration necessary to
achieve maximum extraction efficiency is 1.4×10-6
moL L-1. So the 15×10-6 moL L-1 was used by
ULLME procedure (Fig 3).
Different ionic liquids were used by ULLME
method. Based on Figure 4, maximum extraction
was occurred by [BMIM][PF6]. The high extraction
was observed by volume higher than 0.2 mL for
[BMIM][PF6] (Fig. 4). The effect of sample volume
was evaluated with different volume of blood and
urine samples from 1-25 mL and quantitative
extraction was observed in 10 mL of blood/urine
sample (Fig. 5).
The concentration of Hg(II) based on BPDC as
ligand was determined by ULLME procedure in
blood and human samples which was coupled to
spectrometer of FI-CVAAS. In optimized conditions,
the means of five times determinations, for Hg
(II) were obtained by proposed method. The real
samples were spiked with standard concentration
of Hg(II) in LLOQ and ULOQ of linear range at
pH=7 (Table 1). As validation methodology, the
good accuracy results was achieved by spiking
standard mercury species (0.1-7.0 𝜇g L−1) to human
Fig. 1. Back extraction of Ionic liquid with different acids
Table 1. Instrumental and extraction conditions for
mercury determination by FI- CVAAS
Instrumental Parameters Mercury
Wavelength (nm) 253.7
Lamp current (mA) 3-4
Spectral bandwidth (nm) 0.5
LOD (μg L-1) 0.2
LOQ (μg L-1) 0.6
Working range(μg L-1) 0.5-70
ULLME method by BPDC Mercury
LOD (μg L-1) 0.015
LOQ (μg L-1) 0.05
Working range (μg L-1) 0.05-7.1
Enrichment Factor 9.8
Volume sample (mL) 10
Amount of IL (g) 0.2
pH 7
53
Analysis in occupational health Ali Ebrahimi et al
Fig. 2. Effect of pH on mercury extraction in human blood /urine samples
Fig. 3. Effect of BPDC on mercury extraction in human blood /urine samples
Fig. 4. Effect of sample volume on mercury extraction in human blood /urine samples
54 Analytical Methods in Environmental Chemistry Journal; Vol. 2 (2019)
proposed method for determining blood and urine
mercury was shown by CRM, NIST in Table 2.
Also Statistical parameters for determining
mercury in blood and briefing air sample were
calculated in Table 3. In addition, the results of
mercury concentration in blood samples of worker
and control were shown in Figure 6.
4. Conclusions
Mercury has toxic effect in humans. In high
exposures, observed mostly in occupational
settings, the severity of response correlates with
the duration and intensity of the exposure. Increase
mercury exposure depended on time of working
and volume of air briefing which was determined
based on NIOSH 6009. The results showed us, the
mercury concentration in human blood/urine and
briefing air in workers were higher than control
group. Also, the increasing mercury doses in human
blood and briefing air may be lead to an important
neuropsychological problem in workers. Therefore,
the concentration of mercury in human blood and
briefing air is very important factor that must be
Fig. 5. Effect of ionic liquid on mercury extraction in human blood /urine samples
Table 1. Validation of proposed method for determining
blood mercury by BPDC (μg L-1)
Recovery
(%)
Found
mercury
Added
mercury
Sample
-----2.33± 0.09-----Blood A
96.54.26 ± 0232
98.76.28 ± 0354
-----1.78 ± 0.07-----Blood B
1022..80 ± 0.141
97.53..73 ± 0.182
-----3.12 ± 0.16-----Urine A
101.55.15 ± 0.282
99.06.09 ± 0.323
-----7.45 ± 0.33-----*Urine B
97.412.32 ± 0.655
99.317.38 ± 0.3210
a Mean of five determinations ± confidence interval (P = 0.95)
• Urine diluted with DW(1::5)
Table 2. Analytical results of mercury determination in certified reference material (CRM)
Analyte CRM Certified Value (μg L-1)Found (μg L-1) Recovery%
Mercury NIST SRM 3133 Lot 061204 6.50 ± 0.29 6.38 ± 0.33 98.2
Mean value ± standard deviation based on three replicate measurements.
samples. Mercury concentrations in workers have
higher than threshold limit value (TLV) and all of
them have almost clinical problem. Validation of
55
Analysis in occupational health Ali Ebrahimi et al
controlled and determined in industrial workers. In
this study the precise and accurate method based
on BPDC was used for mercury determination
in blood and urine samples by ULLME coupled
with FI-CVAAS. The experimental showed, the
concentration mercury in worker were higher than
OSHA/ACGHI references.
5. Acknowledgements
Approval was obtained from the Kerman University
of medical science Occupational Health Committee
(R. KUMS.PN: 96.10.60.11712).
6. References
[1] WHO. Elemental Mercury and Inorganic Mercury
Compounds, Human Health Aspects, Concise
International Chemical Assessment Document 50.
World Health Organization, Geneva, 2003.
[2] T. Ohno, M. Sakamoto, T. Kurosawa, M. Dakeishi,
T. Iwata, K. Murata, Total mercury levels in
hair, toenail and urine among women free from
occupational exposure and their relations to renal
tubular function, Environ. Res., 103 (2007)191-
198.
[3] A. Kingman, T. Albertini, LJ. Brown, Mercury
concentrations in urine and whole blood associated
with amalgam exposure in a US military population.
J. Dent. Res., 77 (1998) 461-471.
[4] M.Kampa, E. Castanas, Human health effects of air
pollution, In. Environ Pollut., 151 (2008) 362-367.
[5] LL. Booze, Elemental mercury exposure: an
evidence-based consensus guideline for out-of-
hospital management, Clin. Toxicol., 46 (2008)
21-28.
[6] SC. Foo, Neurobehavioral effects in Occupational
Chemical Exposure. Environ. Res., 60 (1993) 267-
73.
[7] WHO, Mercury environmental aspects, environmental
health criteria. world health organization, Geneva,
2008.
[8] IARC, beryllium, cadmium, mercury and exposures
in the glass manufacturing industry, mercury and
mercury compounds, International Agency for
Research on Cancer, Vol 58, 1997.
Table 3. Statistical parameters for determining mercury in blood and briefing air sample by BPDC
sample Mean Conc. Median Conc. RSD% Range Conc.
a Worker 25.37± 0.93 20.15± 0.57 3.6 4.0-52
a control group 1.15± 0.08 0.94± 0.04 4.2 0.7-5.0
b Worker 32.72± 2.24 29.81± 1.08 2.7 8.0-64
b control group 0.74± 0.03 0.62± 0.02 2.9 0.2-1.1
c Worker 0.045± 0.01 0.038± 0.01 4.4 0.01-0.05
c control group ND ND --- ND
a Blood concentration, BPDC (μg L-1)
b Urine concentration, BPDC (μg L-1)
c Briefing air concentration (mg m-3)
Fig. 6. Dispersive of blood mercury concentration in worker and control group
56 Analytical Methods in Environmental Chemistry Journal; Vol. 2 (2019)
[9] H V. Warren, S J. Horksy, C E Gould, Quantitative
analysis of zinc, copper, lead, molybdenum,
bismuth, mercury and arsenic in brain and other
tissues from multiple sclerosis and non-multiple
sclerosis cases, Sci. Total Environ., 29 (1983) 163-
171.
[10] T W. Clarkson, L. Magos, G J. Myers, The
toxicology of mercury current exposures and
clinical manifestation, New Eng. J. Med., 349
(2003) 1731-1737.
[11] M E. Vahter, N K Mottet, L T. Friberg, S B. Lind,
J S. Charleston, T M. Burbacher, Demethylation of
methyl mercury in different brain sites of Macaca
fascicularis monkeys during long-term subclinical
methyl mercury exposur, Toxicol. Appl. Pharm.,
134 (1995) 273-284.
[12] M B. Pedersen, J C. Hansen, G. Mulvad, H S.
Pedersen, M Gregersen, G. Danscher, Mercury
accumulations in brains from populations exposed
to high and low dietary levels of methyl mercury.
Concentration, chemical form and distribution
of mercury in brain samples. Int. J. Circumpolar
Health, 58 (1999) 96-107.
[13] M. Nylander, L. Friberg, J Weiner, Muscle biopsy as
an indicator for predicting mercury concentrations
in the brain, Br. J. Ind. Med., 47 (1990) 575-576.
[14] G. Turabelidze, Multiple sclerosis prevalence and
possible lead exposure. J. Neurol. Sci., 269 (2009)
158-162.
[15] OSHA, Guidelines for mercury vapor. Occupational
safety and health administration, 2008. Available
at: www.osha-slc.gov
[16] NIOSH, Centers for disease control and prevention.
National Institute for Occupational Safety and
Health, guide to chemical hazards, 3th Ed, 2007.
[17] ACGIH, U.S Documentation of the threshold
limit values and biological exposure. American
Conference of Governmental Industrial Hygienists,
7th Ed, 2011.
[18] N M. Tietz, Clinical Guide to Laboratory Tests. W.
B. Saunders, Philadelphia, PA, 8rd Ed, 2010.
[19] NIOSH, Documentation of the threshold limit
values and biological exposure indices. National
Institute for Occupational Safety and Health,
Cincinnati, OH., 7th Ed., 2001.
[20] Y. Cai, Speciation and analysis of mercury, arsenic,
and selenium by atomic uorescence spectrometry,
TrAC Trends Anal. 19 (2000) 62-66.
[21] Gao, Ying, Determination and speciation of
mercury in environmental and biological samples
by analytical atomic spectrometry, Microchem. J.,
103 (2012) 1-14.
[22] J. Szkoda, J. Zmudzki, A. Grzebalska,
“Determination of total mercury in biological
material by atomic absorption spectrometry
method, J. Bull. Vet. Inst. Pulawy, 50 (2006) 363.
[23] H. Erxleben, R. Jaromir, Atomic absorption
spectroscopy for mercury, automated by sequential
injection and miniaturized in lab-on-valve system,
Anal. Chem., 77.16 (2005) 5124-5128.
[24] W. Peng, H. Liang, Z Chengbin, H. Xiandeng, E S
Ralph, Applications of chemical vapor generation
in non-tetrahydroborate media to analytical atomic
spectrometry, J. Anal. Atom. Spec., 25.8 (2010)
1217-1246.
[25] CF. Harrington, the speciation of mercury and
organomercury compounds by using high-
performance liquid chromatography, TrAC, Trends
Anal. Chem., 19 (2000) 167-179.
[26] CJ, Cappon, J C Smith, Gas-chromatographic
determination of inorganic mercury and
organomercurials in biological materials, Anal.
Chem., 49.3 (1977) 365-369.
[27] SCK. Shum, HM. Pang, RS Houk, Speciation of
mercury and lead compounds by microbore column
liquid chromatography-inductively coupled
plasma mass spectrometry with direct injection
nebulization, Anal. Chem., 64 (1992) 2444-2450.
[28] L. N. Liang, G. B. Jiang, J. F. Liu, J. T. Hu,
Speciation analysis of mercury in seafood by using
high-performance liquid chromatography on-
line coupled with cold-vapor atomic uorescence
spectrometry via a post column microwave
digestion, Anal. Chim. Acta, 477 (2003) 131-137.
[29] X Jia, Y Han, X Liu, T Duan, H Chen, Speciation
of mercury in water samples by dispersive liquid–
liquid microextraction combined with high
performance liquid chromatography-inductively
coupled plasma mass spectrometry, Spectrochim.
Acta Part B: Atom. Spec., 66 (2011) 88-92.
[30] S. Mishra, R. M. Tripathi, S. Bhalke, V. K. Shukla,
V. D. Puranik, Determination of methylmercury
and mercury (II) in a marine ecosystem using
solid-phase microextraction gas chromatography-
mass spectrometry, Anal. Chim. Acta, 551 (2005)
192-198.
57
Analysis in occupational health Ali Ebrahimi et al
[31] Q. Liu, Determination of mercury and
methylmercury in seafood by ion chromatography
using photo-induced chemical vapor generation
atomic uorescence spectrometric detection,
Microchem. J., 95 (2010) 255-258.
[32] M. Park, H. Yoon, C. Yoon, J. Y. Yu, Estimation
of mercury speciation in soil standard reference
materials with different extraction methods by ion
chromatography coupled with ICP-MS, Environ.
Geochem. health, 33 (2011) 49-56.
[33] S. Carneado, R. Peró-Gascón, C. Ibáñez-Palomino,
J. F. López-Sáncheza, A. Sahuquillo, Mercury (II)
and methylmercury determination in water by
liquid chromatography hyphenated to cold vapour
atomic uorescence spectrometry after online
short-column preconcentration, Anal. Method., 7
(2015) 2699-2706.
[34] A. Fashi, MR. Yaftian, A. Zamani, Electromembrane
extraction-preconcentration followed by
microvolume UV–Vis spectrophotometric
determination of mercury in water and sh samples,
Food chem., 221 (2017) 714-720.
[35] D. M, Sánchez, R. Martın, R. Morante, J. Marın,
M.L. MunueraPreconcentration speciation method
for mercury compounds in water samples using
solid phase extraction followed by reversed phase
high performance liquid chromatography, Talanta,
52 (2000) 671-679.
[36] M. Krawczyk, E. Stanisz, Ultrasound-assisted
dispersive micro solid-phase extraction with nano-
TiO2 as adsorbent for the determination of mercury
species, Talanta, 161 (2016): 384-391.
[37] E. Ziaei, A. Mehdinia, A. Jabbari, A novel
hierarchical nanobiocomposite of graphene oxide–
magnetic chitosan grafted with mercapto as a solid
phase extraction sorbent for the determination
of mercury ions in environmental water samples,
Anal. Chim. Acta, 850 (2014) 49-56.
[38] N. Pourreza, K. Ghanemi, Determination of mercury
in water and sh samples by cold vapor atomic
absorption spectrometry after solid phase extraction
on agar modied with 2-mercaptobenzimidazole, J.
Hazard. Mater., 161 (2009) 982-987.
[39] A Krata, K Pyrzyńska, E Bulska, Use of solid-
phase extraction to eliminate interferences in the
determination of mercury by ow-injection CV
AAS, Anal. Bioanal. Chem., 377 (2003) 735-739.
[40] L. Adlnasab, H. Ebrahimzadeh, A. A. Asgharinezhad,
M. Nasiri Aghdam, A. Dehghani, S. Esmaeilpour,
preconcentration procedure for determination of
ultra-trace mercury (II) in environmental samples
employing continuous-ow cold vapor atomic
absorption spectrometry, Food anal. Method., 7
(2014) 616-628.
[41] NH Khdary, AG Howard, New solid-phase-
nanoscavenger for the analytical enrichment of
mercury from water, Analyst, 136 (2011) 3004-
3009.
[42] E. Zolfonoun, A. Rouhollahi, A. Semnani, Solid-
phase extraction and determination of ultra-trace
amounts of lead, mercury and cadmium in water
samples using octadecyl silica membrane disks
modied with 5, 5′-dithiobis (2-nitrobenzoic acid)
and atomic absorption spectrometry, Int. J. Environ.
Anal. Chem., 88 (2008) 327-336.
[43] Y. Date, et al, Trace-level mercury ion (Hg2+)
analysis in aqueous sample based on solid-phase
extraction followed by microuidic immunoassay,
Anal. Chem., 85 (2012) 434-440.
[44] P. Rivaro, C. Ianni, F. Soggia, R. Frache, Mercury
speciation in environmental samples by cold
vapour atomic absorption spectrometry with in situ
preconcentration on a gold trap, Microchim. Acta,
158 (2007) 345-352.
[45] H. Shirkhanloo, A. Khaligh, H. Zavvar Mousavi,
M. M. Eskandari, A. A. Miran-Beigi, Ultra-trace
arsenic and mercury speciation and determination
in blood samples by ionic liquid-based dispersive
liquid-liquid microextraction combined with ow
injection-hydride generation/cold vapor atomic
absorption spectroscopy, Chem. Paper.. 69 (2015)
779-790.
[46] N. Rajesh, G. Gurulakshmanan, Solid phase
extraction and spectrophotometric determination of
mercury by adsorption of its diphenylthiocarbazone
complex on an alumina column, Spectrochim. Acta
Part A: Mol. Biomol. Spec., 69.2 (2008) 391-395.
[47] HI. Ulusoy, R Gürkan, S Ulusoy, Cloud point
extraction and spectrophotometric determination
of mercury species at trace levels in environmental
samples, Talanta, 88 (2012) 516-523.
[48] J. C. de Wuilloud, R. G. Wuilloud, M. F. Silva, R.A.
Olsina, L. D. Martinez, Sensitive determination
of mercury in tap water by cloud point extraction
pre-concentration and ow injection-cold vapor-
inductively coupled plasma optical emission
58 Analytical Methods in Environmental Chemistry Journal; Vol. 2 (2019)
spectrometry, Spectrochim. Acta Part B: Atom.
Spec., 57 (2002) 365-374.
[49] A. Nasrollahpour, S. M. J. Moradi, S. E. Moradi.
Dispersive solid phase micro-extraction of mercury
(II) from environmental water and vegetable
samples with ionic liquid modied graphene oxide
nanoparticles, J. Serb. Chem. Soc., 82 (2017) 551-
565.
[50] C. Mitani, A. Kotzamanidou, A.N. Anthemidis,
Automated headspace single-drop microextraction
via a lab-in-syringe platform for mercury
electrothermal atomic absorption spectrometric
determination after in situ vapor generation, J.
Anal. Atom. Spec., 29 (2014) 1491-1498.
[51] M. Hossien-poor-Zaryabi, et al. “Application of
dispersive liquid–liquid micro-extraction using
mean centering of ratio spectra method for trace
determination of mercury in food and environmental
samples. Food Anal. Method., 7 (2014) 352-359.
[52] M. Rezaee, Y. Assadi, M. R. M. Hosseini, E.
Aghaee, F. Ahmadi, S. Berijani, Determination
of organic compounds in water using dispersive
liquid–liquid microextraction, J. Chromatogr. A,
1116 (2006) 1-9.
[53] G. Li, K. H. Row, Utilization of deep eutectic
solvents in dispersive liquid-liquid micro-
extraction, TrAC, Trends Anal. Chem., 120 (2019)
115651.
[54] Li, Yanyan, et al, Magnetic effervescent tablet-
assisted ionic liquid-based dispersive liquid-liquid
microextraction of polybrominated diphenyl ethers
in liquid matrix samples, Talanta, 195 (2019) 785-
795.
