Determination of Triclocarban, Triclosan and Methyl-Triclosan in Environmental Water by Silicon Dioxide/Polystyrene Composite Microspheres Solid-Phase Extraction Combined with HPLC-ESI-MS

doi:10.4236/gep.2013.12003

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Journal of Geoscience and Environment Protection

2013. Vol.1, No.2, 13-17

Published Online October 201 3 in SciRes (http://www.scirp.org/journal/gep) http://dx.doi.org/10.4236/gep.2013.12003

Determination of Triclocarban, Triclosan and Methyl-Triclosan in

Environmental Water by Silicon Dioxide/Polystyrene Composite

Microspheres Solid-Phase Extraction Combined with

HPLC-ESI-MS

Yinan Wang1,2, Pengfei Li1,3, Yan Liu1, Bing Chen1, Jinyu Li1, Xikui Wang1*

1School of Chemical Engineering, Shandong Polytechnic University, Jinan, China

2School of Biological Science and Technology, Beijing Forestry University, Beijing, China

3Jinan Water Group Company Limited, J inan, China

Email: *[email protected]

Received July 2013

This paper developed a sensitive and efficient analytical method for triclocarban (TCC), triclosan (TCS)

and Methyl-triclosan (MTCS) determination in environmental water, which involves enrichment by using

silicon dioxide/polystyrene composite microspheres solid-phase extraction and detection with HPLC-

ESI-MS. The influence of several operational parameters, including the eluant and its volume, the flow

rate and acidity of water sample were investigated and optimized. Under the optimum conditions, the lim-

its of detection were 1.0 ng/L, 2.5 and 4.5 ng/L for TCC, TCS, and MTCS, respectively. The linearity of

the method was observed in the range of 5 - 2000 ng/L, with correlation coefficients (r2) > .99. The spiked

recoveries of TCC, TCS and MTCS in water samples were achieved in the range of 89.5% - 96.8% with

RSD below 5.7%. The proposed method has been successfully applied to analyze real water samples and

satisfactory results were achieved.

Keywords: Triclocarban; Triclosan; Solid-Phase Extraction; Silicon Dioxide/Polystyrene Composite

Microspheres; HPLC-ESI-MS/MS

Introduction

Over the past decades, increasing residues of pharmaceuti-

cals and personal care products (PPCPs) have been detected in

the aquatic environment. Hundreds of tones of these com-

pounds are dispensed in communities every year. The conti-

nuous input of such compounds may affect water quality and

potentially affect the ecosystem and human health (Halden &

Paull, 2005; Ahn et al., 2008; Chalew & Halden, 2009). Tric-

locarban (N-(4-chlorophenyl)-N-(3,4-dichlorophenylurea, TCC)

and triclosan (5-chloro -2-(2, 4-dichloro-phenoxy)-phenol, TCS)

are both antimicrobials that are added to a wide range of

household and personal-care products, such as shampoos, soaps,

creams, mouthwash and toothpaste. However, TCC has harmful

effects on humans and other animals because it increases me-

themoglobinemia (Ponte et al., 1974). TCC exposure enhances

the estradiol-dependent or testos-terone-dependent activation of

the estrogen receptor-responsive and the androgen receptor-

responsive gene expression in human ovary cells (Ahn et al.,

2008). Moreover, TCC affects the transcription of genes that

respond to the thyroid hormone in frog and rat cells (Hinther et

al., 2011). Bioaccumulation studies have shown that TCC ac-

cumulates in algae (Coogan et al., 2007) and snails (Coogan et

al., 2008). Similarly, TCS was found to be acutely toxic to a

number of aquatic organisms, particularly for algae species, and

was recently shown to the modulate thyroid function of amphi-

bians at concentrations as low as .15 μg/L (Orvos et al., 2002).

In addition, triclosan has been shown to phototransform into

chlorinated dibenzodioxins (Mezcua et al., 2004). Methyl-tric-

losan (MTCS) is a metabolite of TCS. It is more lipophilic and

environmentally persistent (Chu & Metcalfe, 2007; Coogan et

al., 2007), suggesting its relatively high bioaccu-mulation po-

tential in aquatic organisms (Coogan et al., 2007).

The potential risk to the environment and human health gen-

erated by TCC, TCS and MTCS is currently drawing consider-

able attention worldwide. Therefore, it is very essential to es-

tablish simple, sensitive and reliable analytical method to de-

termine these compounds in various environmental water sam-

ples for safety evaluation.

Generally, a sample enrichment and clean-up procedure are

often needed prior to the instrumental determination because

these pollutants are present at very low levels in environmental

water samples (μg/L or less). Many sample pretreatment me-

thods, such as liquid-liquid extraction (LLE) (Canosa et al.,

2007; Sun et al., 2012), dispersive liquid-liquid microextraction

(DLLME) (Guo et al., 2009; Zhao et al., 2011), solid-phase ex-

traction (SPE) (Halden & Paull, 2004; Sapkota et al., 2007),

solid-phase micro-extraction (SPME) (Montes et al., 2005),

hollow fiber assisted liquid-phase microextraction (HF-LPME)

(Zhao et al., 2007), and stir bar sorptive extraction (SBSE) (Ka-

waguchi et al., 2008) have been used for the enrichment of TCS

and TCC.

Traditional LLE is widely used as a sample preparation tech-

nique by several authors (Liska et al., 1989), but it is tedious,

time consuming, costly and needs large volumes toxic and

*Corresponding author.

Y. N. WANG ET AL.

flammable solvents. SPME has drawbacks of high cost, sample

carry-over, and a decline in performance with time. LPME

produces some obvious disadvantages: solvent drops are ready

to break, air bubble is tending to form, time is long and some-

times equilibrium is not achieved easily in short time (Melwan-

ki & Fuh, 2008).

SPE has extinguished from many extraction techniques and

has been widely used for the concentration and measurement of

many pollutants (Halden & Paull, 2004; Chu & Metc alfe, 2007;

Sapkota et al., 2007). SPE has been an effective sample-hand-

ing technique with many obvious advantages such as high re-

covery, high pre-concentration factors, low consumption of or-

ganic solvents, simplicity, easy operation and automation. In

SPE the analytes to be extracted are partitioned between a solid

and liquid and these analytes must have a greater affinity for

the solid phase than for the same matrix, which are better than

the two immiscible liquids as in LLE. The different mechan-

isms of retention or elution are due to inter-molecular forces

between the analytes, the active sites on the surface of the ad-

sorbent and liquid phase or matrix. Therefore, the types of the

adsorbents are the key to SPE process.

The silicon dioxide/polystyrene composite microspheres (SiO2/

PS) is a mixed-mode sorbent which was prepared through po-

lymerization of styrene on the surface of SiO2. It has both a

hydrophilicity of SiO2 and a lipophilicity of polystyrene, and

was successfully used to extract nitrophenol and alkylphenol

from aqueous environmental samples (Shen S. C. et al., 2012).

Sensitive and selective approaches for determination of TCC,

TCS and MTCS have been established, including GC/MS (Coo-

gan et al., 2007; Kawaguchi et al., 2008)], GC/MS/MS (Boeh-

mer et al., 2004), LC/MS (Chu & Metcalfe, 2007; Sapkota et al.,

2007) and LC/MS/MS (Zhao et al., 2011; Shen J. et al., 2012).

In order to reduce complex derivatization step and possible in-

terferences of other compounds, HPLC-ESI-MS was selected

for the sensitive determination of TCC, TCS and MTCS be-

cause they are compounds with strong polarity.

The aim of this work is to develop a rapid SPE-UHPLC-MS

method for simultaneous dete rmination of T CC, T CS and MTCS

in environmental water samples. To accomplish its application

in environmental monitoring of environmental water, silicon

dioxide/polystyrene (SiO2/PS) SPE cartridges was selected for

the pre-concentrations. A series of key parameters influencing

the enrichment efficiency of TCC, TCS and MTCS have been

investigated and optimized. It could provide enough valid evi-

dence for post-study .

Materials and Methods

Materials

HPLC-grade methanol, acetonitrile, and acetone were pur-

chased from Tedia Company Inc. (Fairfield, Ohio, USA). TCC

were purchased from Dajie Technical Co. Ltd. (Hunan, China).

TCS and MTCS were obtained from Dr. Ehrenstorfer (Augs-

burg, Germany). Standard stock solution of TCC, TCS and

MTCS (100 mg∙L) was prepared in methanol and then stored at

4˚C. Fresh working solutions were prepared daily by diluting

the stock solution with purified water. The SiO2/PS sorbent (5

μm) was obtained from Lantian Pharmaceutical co. Ltd. (Wu-

han, China).

A SiO2/PS packed cartridge was prepared by modifying an

Agilent cleanert ODS C18 cartridge (70 mm × 14 mm, 6 mL,

polypropylene), which was purchased from Agilent Techno-

logies (Palo Alto, CA,USA). 500 mg of SiO2/PS sorbent was

packed into the cartridge, after the C18 packing was evacuated.

The polypropylene upper frit and lower frit were placed at each

end of the cartridge to hold the SiO2/PS packing fixed. Then the

bottom end of the cartridge was connected to a SHBIII vacuum

pump (Great Wall Scientific and Trade Co. Ltd., Zhengzhou,

Henan), and the upper end of cartridge was connected with a

PTFE suction tube, the other end of which was immersed into

the water sample. The whole SPE device was washed by suffi-

cient methanol and purified water before the first usage, in

order to avoid the pollution of organic contaminants.

Instruments

The high-performance liquid chromatography-mass spectro-

metry equipment was an Agilent 1100 LC system, including an

electrospray ionization mass spectrometer (ESI-MS), a quater-

nary pump, a column thermostat, and an automatic sample in-

jector with a 100 μL loop. A personal computer equipped with

the Agilent ChemStation program for HPLC-MS was used to

process the chromatographic data. An Agilent Eclipse XDB-C8

column, 4.6 mm × 150 mm, 5 μm particle size, was used to

held at 30˚C to analyze TCS. The injected sample volume was

10 μL, and the binary mobile phase was composed of 25%

water and 75% methanol (v/v) at a constant flow rate of .8

mL/min. Under these chromatographic conditions, one HPLC-

MS run can be finished within 10 min. MS conditions were

maintained as follows: drying gas 10.0 L/min; nebulizer pres-

sure 30 psi; chemcur. .32 μA; quadratic temperature 99˚C; high

vac. 1.1 × 10−5 Torr. Target compounds analysis was carried

out in negative ionization mode and quantification was per-

formed under SIM conditions.

SPE Proc edu re

The cartridge packed with SiO2/PS adsorbent was condition-

ed with 10 mL of methanol in acetone (50%), followed by 5

mL of methanol and 5 mL of water before use. Aliquots (300

mL) of water sample were passed through the cartridges at a

flow rate of approximately 10 mL/min. Following the loading

of the sample, the cartridge was eluted with 5 mL hexane, and 5

mL dichloromethane to remove the co-adsorbed matrix sub-

stance. After the cartridge was dried with a vacuum, 2 × 5 mL

of 5% methanol in water was used to wash it. Then the car-

tridge was dried under vacuum for 10 min. The cartridge was

eluted with 3 × 5 mL methanol in acetone (50%) at a slow rate

of 1 mL/min. The combined extract was dried under N2 gas a nd

then reconstituted in .5 mL of methanol.

Results and Discussion

Method Development

Selection of the Adsorbents

SPE has gained popularity as a technique for the extraction

of polar to medium-polarity analytes from aqueous environ-

mental samples. With a number of different sorbents applied in

SPE and all kinds of commercial SPE cartridges emerged in the

market, SPE can almost meet all the demands of preconcentra-

tions and clean-up in the environmental monitoring. The reco-

veries of TCC, TCS and MTCS were investigated by using four

different SPE cartridges: Agilent SampliQ Optimised Polymer

technology (OPT), Agela Cleanert PEP, bamboo-activated char-

Y. N. WANG ET AL.

coal (BAC) and SiO2/PS with eluate of 50% methanol in ace-

tone. As shown in Figure 1, the experimental results indicate

that the OPT sorbent is unsuitable for the isolation of TCC,

TCS and MTCS because of its poor recoveries. The Agela

Cleanert PEP and the BAC sorbents showed efficient selective

adsorption for TCC, TCS and MTCS, respectively. However,

these SPE cartridges are unsuitable for the simultaneous deter-

mination of all three analytes. Only the SiO2/PS sorbent showed

satisfactory recoveries for TCC, TCS and MTCS and was thus

selected to be the SPE material in this study.

Selection of the Eluant and Its Volume

Eluant is a key parameter that affects the recovery of target

compounds. Three eluants, including methanol, acetone, and

50% methanol in acetone, were tested. The results indicate that

50% methanol in acetone has better desorption efficiencies (the

recoveries were 91.2%, 94.5% and 96.0% for TCC, TCS and

MTCS, respectively), as shown in Figure 2. Therefore, 50%

methanol in acetone was chosen as the eluant.

Then the effect of eluant volume which directly affects the

recovery of analytes was investigated. A series of experiments

were designed and performed by changing the volumes of elu-

ant over the range of 2.3 - 15.0 mL. The results showed that the

recoveries TCC, TCS and MTCS increased with the increase of

the eluant volume between 3.0 mL and 9.0 mL (Figure 3).

When the volume is more than 9.0 mL, the extraction efficien-

cies of TCC, TCS and MTCS almost kept constant. Therefore,

9.0 mL eluant was used as the eluant in all subsequent experi-

ments.

Influence of pH

To examine the effect of the pH of the water sample on the

Figure 1.

Effect of adsorbents on the recoveries of TCC, TCS

and MTCS.

Figure 2.

Effect of eluant on the recoveries of TCC, TCS and

MTCS.

recoveries of TCC, TCS and MTCS, a series of experiments

were performed by changing the pH of the water samples from

2.0 to 13.0, as shown in Figure 4. The result indicates that the

recoveries of TCC, TCS and MTCS maintain high from pH 2 to

pH 10. However, under the condition of alkalinity, the recovery

of TCC kept satisfactory while that of TCS and MTCS dropped

dramatically. This result may possibly be attributed to the struc-

tural characteristics of TCS. Strong alkalinity may result in the

deprotonation of the hydroxyl of TCS and MTCS, which af-

fects their solubility in water. According to these experimental

results, the pH of solutions was adjusted in the range from 4.0

to 6.0 in the subsequent experiments.

Influence of Flow Rate

The flow rate of water sample affects the recovery of TCS

and controls the sample pretreatment time. Here, the flow rates

of the sample were optimized in the range of 1.0 - 3.0 mL /min

with the limitation on the negative pressure of the pump. The

results from Figure 5 show that the flow rate had no obvious

influence on the extraction efficiency of TCC, TCS and MTCS.

In order to save extraction time, the highest flow rate, 3.0

mL/min, was adopted in the following experiments

Method Validation

Under the given optimal conditions, a number of important

parameters of the method, such as linearity range, correlation

coefficient (r2), reproducibility, limit of detection, and recovery,

were studied. Linearity was tested by varying the concentra-

tions of TCC, TCS and MTCS from 5 ng/L to 20,000 ng/L,

Figure 3.

Effect of volume of eluant on the recoveries of TCC,

TCS and MTCS.

Figure 4.

Effect of pH of samples on the recoveries of TCC,

TCS and MTCS.

MenthanolAcetone Menthanol/Acetone

100

120

Recoveries(%)

TCC

TCS

MTCS

2 4 6 810 12 14 16

100

110

Recovery (%)

Volume of eluant

TCC

TCS

MTCS

246810 12 14

100

Recoveri es (%)

pH value

TCC

TCS

MTGS

Y. N. WANG ET AL.

Figure 5.

Effect of flow rate on the recoveries of TCC, TCS

and MTCS.

with r2 > .99. Limits of detection (LOD) of the analytes were

calculated with signal/noise ratios (S/N) of 3. Limits of quanti-

fication (LQD) were calculated with signal/noise ratios (S/N) of

10. Detailed information on the limits of the analytes was pro-

vided in Table 1.

To investigate the effects of the sample matrix, two water

samples collected from Xiaoqing River were spiked with TCC,

TCS and MTCS at different levels and were then analyzed. The

recoveries of spiked water are listed in Table 2. The effects of

the matrix on the signal were insignificant after sample clean-

up by using SPE.

Determination of TCC, TCS and MTCS in

Environmental Water Samples

For a preliminary survey and for method validation, the me-

thod developed was used for simultaneous analysis of the three

target compounds in a variety of environmental water samples.

Three river water samples were collected in Xiaoqing Rivers in

Jinan area, Shandong Province, China. The sample 1# was col-

lected in the upstream of the wastewater treatment plant, .5 km

from the discharge port. The sample 2# was collected in the

downstream of wastewater treatment plant near the discharge

port, and samples 3# was collected downstream of wastewater

treatment plant, apart from the discharge port 2 km. Two sea

water samples collected in Yellow Sea at Qingdao port. Sample

1# was from the coast, and sample 2# was 2 km apart from the

coast. Figure 6 shows a typical HPLC-ESI-MS chromatogram

obtained from a river water extract. The average concentrations

of the target compounds in a variety of environmental water

samples are listed i n Table 3.

Conclusion

A procedure for the determination of TCC, TCS and MTCS

in environmental water samples is developed. The analytes

were simultaneously isolated using silicon dioxide/polystyrene

composite microspheres SPE sorbent, and then they were de-

termined with UHPLC-ESI-MS. Under the optimized condi-

tions, the LODs were 1.0 ng/L, 2.5 ng/L and 4.5 ng/L for TCC,

TCS and MTCS, respectively. The spiked recoveries of TCC,

TCS and MTCS in environmental water samples were achieved

in the range of 89.5% - 96.8% with RSD below 5.7%. With this

method, the TCC, TCS and MTCS in a variety of environmen-

tal water samples from Xiaoqing Rivers and Yellow Sea were

detected. This work indicates that the proposed method is con-

Table 1.

Linear range and limits of detection of the method.

Analyte Liner range (ng/L) r2 LOD LOQ

TCC

TCS

MTCS

5 - 2000

.996

.994

.997

1.0

2.5

4.5

3.5

8.0

14.0

Table 2.

Experimental recoveries of TCC, TCS and MTCS from spiked real

water samples.

Analyte Found (ng/L) Added (ng/L) Recovery (%) RSD (%)

TCC

TCS

MTCS

136

NDa

200

89.5

93.4

93.8

95.6

96.8

94.2

5.2

3.8

4.9

5.7

3.3

3.9

Note: aNot detecte d.

Figure 6.

Typical HPLC-ESI-MS chromatogram obtained

from river water.

Table 3.

Analytical results of TCC, TCS and MTCS in environmental water

sa mp le s .

SAmples TCC (ng/L) TCS (ng/L) MTCS (ng/L)

Xiaoqing Ri ver

Sea water

326

136

245

NDa

Note: aNot detecte d.

venient and reliable for the determination of TCC, TCS and

MTCS in environmental water samples. This method could be

applied to monitor TCC, TCS in various environmental water

samples.

Acknowledgements

The authors are thankful to the financially supports by the

National Natural Science Foundation of China (No. 21077069).

REFERENCES

Ahn, K. C., Zhao, B., Chen, J., Cheredenichenko, G., Sanmarti, E., &

Denision, M. S. (2008). In vitro biological activities of the antimi-

crobials triclocarban, its analog ues, and triclosan in bioassay screens:

Receptorbased bioassay screens. Environmental Health Perspectives,

116, 1203-1210.

123

100

120

Recoveries (%)

Flow rate (mL/min)

TCC

TCS

MTCS

Y. N. WANG ET AL.

http://dx.doi.org/10.1289/ehp.11200

Boehmer, W., Ru edel, H. , Wenzel, A ., & Schroeter-Kermani, C. (2004).

Retrospective monitoring of triclosan and methyl-triclosan in fish:

Results from the German environmental specimen bank. Organo-

halogen Compounds, 66, 1516-1521.

Canosa, P., Pérez-Palacios, D., Garrido-López, A., Ten a, T. M., Rodrí-

guez, I., Rubi, E., & Cela, R. (2007). Pressurized liquid extraction

with in-cell clean-up followed by gas chromatography-tandem mass

spectrometry for the selective determination of parabens and triclo-

san in indoor dust. Journal of Chromatography A, 1161, 105-112.

http://dx.doi.org/10.1016/j.chroma.2007.05.089

Chalew, T. E. A., & Halden, R. U. (2009). Environmental exposure of

aquatic and terrestrial bio ta to triclos an and triclocarban. The Journal

of the American Water Resources Association, 45, 4-13.

http://dx.doi.org/10.1111/j.1752-1688.2008.00284.x

Coogan, M. A., Edziyie, R. E., La Point, T. W., & Venable, B. J. (2007).

Algal bioaccumulation of triclocarban , triclosan, and methyl-tri- clo-

san in a North Texas wastewater treatment plant receiving stream.

Chemosphere, 67, 1911-1918.

http://dx.doi.org/10.1016/j.chemosphere.2006.12.027

Coogan, M. A., & La Point, T. W. (2008). Snail bioaccumulation of

triclocarban, triclosan, and methyltriclosan in a north texas, USA,

stream affected by wastewa ter treatment plant runo ff. Environmental

Toxicology and Chemistry, 27, 1788-1793.

http://dx.doi.org/10.1897/07-374.1

Chu, S., & Metcalfe, C. D. (2007). Simultaneous determination of tri-

clocarban and triclosan in municipal biosolids by liquid chromato-

graphy tandem mass spectrometry. Journal of Chromatography A,

1164, 212-218. http://dx.doi.org/10.1016/j.chroma.2007.07.024

Guo, J. H., Li, X. H., Cao, X. L., Li, Y., Wang, X. Z., & Xu, X. B.

(2009). Determination o f triclosan, triclocarban and methyl-triclosan

in aqueous samples by dispersive liquid-liquid microextraction com-

bined with rapid liquid chromatography. Journal of Chromatography

A, 1216, 3038-3043. http://dx.doi.org/10.1016/j.chroma.2009.02.021

Halden, R. U., & Paull, D. H. (2004). Anal ysis of triclocarban in aqua-

tic samples by liquid chromatography electrospray ionization mass

spectrometry. Environmental Science and Technology, 38, 4849-

4855. http://dx.doi.org/10.1021/es049524f

Halden, R. U., & Paull, D. H. (2005). Co-occurrence of triclocarban

and triclosan in US water resources. Environmental Science and

Technology, 39, 1420-142. http://dx.doi.org/10.1021/es049071e

Hinther, A., Bromba, C. M., Wulff, J. E., & Helbing, C. C. (2011).

Effects of triclocarban, triclosan, and methyl triclosan on thyroid

hormone action and stress in frog and mammalian culture systems.

Environmental Science and Technology, 45, 5395-5402.

http://dx.doi.org/10.1021/es1041942

Kawaguchi, M. , Ito, R., H onda, H., Endo, N., Ok anouch i, N., Saito, K .,

Seto, Y., & Nakazawa, H. (2008). Stir bar sorptive extraction and

thermal desorption-gas chromatography-mass spectrometry for trace

analysis of triclosan in water sample. Journal of Chromatography A,

1206, 196-199. http://dx.doi.org/10.1016/j.chroma.2008.08.060

Liska, I., Krupcik, J., & Leclercp, P. A. (1989). The use of solid sor-

bents for direct accumulation o f organic compounds from water ma-

trices-a review of solid-phase ex traction techniques. Journal of High

Resolution Chromatography, 12, 577-590.

http://dx.doi.org/10.1002/jhrc.1240120903

Melwanki, M. B., & Fuh, M. R. (2008). Dispersive liq uid-liquid micro-

extraction combined with se mi-automated in-syringe back extraction

as a new approach for the sample preparation of ionizable organic

compounds prior to liquid chromatography. Journal of Chromato-

graphy A, 1198, 1-6. http://dx.doi.org/10.1016/j.chroma.2008.05.007

Mezcua, M., Gomez, M. J. , Ferrer, I., Agu era, A., Hernand o, M. D., &

Fernandez-Alba, A. R. (2004). Evidence of 2,7/2,8-dibenzodichloro-

p-dioxin as a photodegradation product of triclosan in water and

wastewater samples. Analytica Chimica Acta, 524, 241-247.

http://dx.doi.org/10.1016/j.aca.2004.05.050

Montes, R., Rodríg uez, I., Ru bí, E., & Cela, R. (20 05). Optimization of

solid-phase microextraction conditions for the determination of tric-

losan and possible related compounds in water samples. Journal of

Chromatography A, 1072, 107-115.

http://dx.doi.org/10.1016/j.chroma.2004.11.032

Orvos, D. R., Versteeg, D. J., Inauen, J., Capdeveille, M., Rothenstein

A., & Cunningham, V. (2002). Aquatic toxicity of triclosan. Environ-

mental Toxicology and Chemistry, 21, 1338-1349.

http://dx.doi.org/10.1002/etc.5620210703

Ponte, C., Richard, J., Bonte, C., Lequien, P., & Lacombe, A. (1974).

Methemoglobinemia in Newborn-Discussion of Etiological Role of

Trichlorocarbanilide. Semaine Des Hopitaux, 50, 359-365.

Sapkota, A., Heidler, J., & Halden, R. U. (20 07). Detect ion of triclo car-

ban and two co-contaminating ch lorocarbanilides in US aquatic en vi-

ronments using isotop e dilution liquid chromatography tandem mass

spectrometry. Environmental Research, 103, 21-29.

http://dx.doi.org/10.1016/j.envres.2006.03.006

Shen, J. Y., Chang, M. S., Yang, S. H., & Wu, G. J. (2012). Simulta-

neous determination of triclosan, triclocarban, and transformation

products of triclocarban in aqueous samples using solid-phase mi-

cro-extraction-HPLC-MS/MS. Journal of Separation Science, 35,

2544-2552. http://dx.doi.org/10.1002/jssc.201200181

Shen, S. C., Bi, J. N., Sui, L. L., & Liu, Y. H, (2012). Preparation of

SiO2/PS composite microsphere and its application as solid-phase

extraction sorbent. Chinese Journal of Analysis Laboratory, 31,

51-54.

Sun, J., Yi, C. L., Zh ao, R. S., Wang, X., Jian g, W. Q., & Wang, X. K .

(2012). Determination of trace triclosan in environmental water by

microporous bamboo-activated charcoal solid-phase extraction com-

bined with HPLC-ESI-MS. Journal of Separation Science, 35, 2781-

2786. http://dx.doi.org/10.1002/jssc.201200328

Zhao, R., Cheng, C., Yuan, J., Jiang, T., Wang, X., & Lin, J. (2007).

Sensitive measurement of ultratrace phenols in natural water by

purge-and-trap with in situ acetylation coupled with gas chromato-

graphy-mass spectrometry. Analytical and Bioanalytical Chemistry,

387, 687-694. http://dx.doi.org/10.1007/s00216-006-0890-7

Zhao, R. S., Wang, X., Sun, J., Hu, C., & Wang, X. K. (2011). Determi-

nation of triclosan and triclocarban in environmental water samples

with ionic liquid/ionic liquid dispersive liquid-liquid micro-extrac-

tion prior to HPLC-ESI-MS/MS. Microchimica Acta, 174, 145-151.

http://dx.doi.org/10.1007/s00604-011-0607-2