ORIGINAL PAPER

Determination of triclosan and triclocarbanin environmental water samples with ionic liquid/ionic liquiddispersive liquid-liquid microextraction priorto HPLC-ESI-MS/MS

Ru-Song Zhao & Xia Wang & Jing Sun & Cong Hu &

Xi-Kui Wang

Received: 11 January 2011 /Accepted: 12 April 2011 /Published online: 28 April 2011# Springer-Verlag 2011

Abstract A hydrophobic ionic liquid was finely dispersedin aqueous solution along with a hydrophilic ionic liquid.Following centrifugation, the two phases aggregate to formrelatively large droplets. Based on this phenomenon, amethod termed ionic liquid/ionic liquid dispersive liquid-liquid microextraction was developed. It was applied to theenrichment of triclosan (TCS) and triclocarban (TCC) fromwater samples prior to HPLC with electrospray tandem MSdetection. The type and volume of the hydrophobic ionicliquid (the extraction solvent) and the hydrophilic ionicliquid (the disperser solvent), salt content, and extractiontime were optimized. Under optimum conditions, themethod gives a linear response in the concentration rangesfrom 0.5 to 100 μg L−1 for TCC and from 2.5 to 500 μgL−1 for TCS, respectively. The limits of detection are 0.23and 0.35 μg L−1, and the repeatability is 5.4 and 6.4% forTCC and TCS, respectively. The method was validated withfour environmental water samples, and average recoveriesof spiked samples were in the range from 88% to 111%.The results indicate that the method is a promising newapproach for the rapid enrichment and determination oforganic pollutants.

Keywords Triclosan . Triclocarban .Water samples . Ionic

liquid/ionic liquid dispersive liquid-liquid microextraction .

High-performance liquid chromatography-electrospraytandem mass spectrometry

Introduction

Bactericides, such as triclosan (5-chloro-2-[2.4-dichloro-phe-noxy]-phenol) and triclocarban (N-(4-chlorophenyl)-N’-(3,4-dichlorophenyl)urea), are widely used in household andpersonal-care products, for example shampoos, soaps, creams,mouthwash, and toothpaste [1, 2]. Large consumption (0.6~10 million kg year −1) and frequent detection of TCS andTCC in both waste waters and surface waters have attractedgreat attention worldwide because of the formation of toxicdegradation products of TCS and the potential of TCC to actas an endocrine-disrupting compound [2–4]. Therefore, it isnecessary to establish simple, sensitive and reliable analyticalmethods to determine them in environmental samples forsafety evaluation.

Chromatographic techniques, including GC and HPLC,have long been the most important analytical methods fordetermining TCC and TCS [2, 5–8]. HPLC or HPLC/MShas been shown to be superior to GC or GC/MS, and is afrequently reported technique for the measurement of TCCand TCS because it does not need prior derivatization [2, 4,8]. However, low concentrations of TCC and TCS in realwater samples make direct determination difficult. Sampleenrichment steps prior to instrumental analysis are usuallynecessary.

Nowadays, many developed sample enrichment meth-ods for TCC and TCC such as liquid–liquid extraction,solid-phase extraction, solid-phase microextraction,

R.-S. Zhao (*) :X. Wang : J. Sun : C. HuKey Laboratory for Applied Technology of SophisticatedAnalytical Instruments of Shandong Province,Analysis and Test Center, Shandong Academy of Sciences,Jinan 250014, Chinae-mail: zhaors1976@126.com

J. Sun :X.-K. WangShandong Institute of Light Industry,Jinan 250353, China

Microchim Acta (2011) 174:145–151DOI 10.1007/s00604-011-0607-2

liquid-phase microextraction (LPME) and so on, havebeen used for the enrichment of TCS and TCC inenvironmental water samples [9–12]. Among thesesample pretreatment techniques, LPME is a new sampleenrichment technique that has merits such as simplifica-tion, rapidness and miniaturization. Dispersive liquid-liquid microextraction (DLLME), one of most recentlydeveloped LPME techniques, is based on a ternarycomponent solvent system similar to homogeneous LLEand cloud point extraction [13, 14]. This technique hasmany merits such as high enrichment factor, simplicity,rapidness, and low consumption [13, 14]. It has beenwidely used for the determination of polycyclic aromatichydrocarbons (PAHs) [13], organophosphorus pesticides(OPPs) [14], palladium [15], medroxyprogesterone [16],and so on. DLLME has many merits, however, toxicorganic solvents such as chlorobenzene, chloroform, orcarbon tetrachloride are often used in the extractionprocedure. To reduce exposure danger to toxic organicsolvent for the operator, a new LPME technique termedionic liquid dispersive liquid-phase microextraction (IL-DLPME) has been developed for the rapid enrichment ofTCS and TCC in environmental water samples. In IL-DLPME, instead of using toxic extraction solvents, ionicliquid [C6MIM][PF6] was used as a green extractionsolvent [4]. Hydrophobic ionic liquid could be dispersedinto infinite droplets under driving of high temperature,and then they can aggregate as big droplets at lowtemperature [17]. Based on this phenomenon, anthernovel dispersive liquid-phase microextraction method,termed temperature-controlled ionic liquid dispersiveliquid-phase microextraction (TCIL-DLPME), has beenalso developed for the enrichment and sensitive determi-nation of TCS and TCC in environmental water samples[7]. This method used only green solvent 1-hexyl-3-methylimidazolium hexafluorophosphate as extractionsolvent and overcame the demerits of the use of toxicsolvents and the instability of the suspending drop insingle drop liquid-phase microextraction.

The goal of this paper was to develop a new andsimple method for rapid enrichment and determination ofTCS and TCC in environmental water samples based onIL/IL-DLLME and HPLC-ESI-MS-MS. In IL/IL-DLLMEprocedure, a hydrophobic ionic liquid and a hydrophilicionic liquid were used as extraction solvent and dispersersolvent, respectively. Triclosan and triclocarban wereeasily concentrated into the hydrophilic ionic liquid.Important factors that may affect the enrichment effi-ciencies, such as type and volume of hydrophobic ionicliquid (extraction solvent), type and volume of hydro-philic ionic liquid (disperser solvent), extraction time,sample pH and NaCl content, were investigated andoptimized in detail. In order to validate the applicability

of the developed method, it was used for rapidenrichment and analysis of TCS and TCC in real watersamples such as tap water, river water, snow water andlake water samples.

Experimental

Reagents and chemicals

TCS (99.5%) was purchased from Dr. Ehrenstorfer (www.ehrenstorfer.com) and TCC (≥98%) was obtained fromDajie Scientific and Technological company (www.djkj.com.cn). 1-Butyl-3-methylimidazolium hexafluorophos-phate [C4MIM][PF6] (99%), 1-hexyl-3-methylimidazoliumhexafluorophosphate [C6MIM][PF6] (99%),1-octyl-3-meth-ylimi dazolium hexafluorophosphate [C8MIM][PF6] (99%),1-butyl-3-methylimidazolium tetrafluoroborate [C4MIM][BF4] (99%), 1-ethyl-3-methylimidazole tetrafluoroborate[EMIM][BF4] (99%) and 1-butyl-3-methylimidazoliumnitrate [C4MIM]NO3 (99%) were purchased from ChengjieChemical Company (www.shyfhx.com) and used asobtained. HPLC-grade methanol was obtained from Tedia(www.tedia.com). All the other reagents were analyticalgrade unless otherwise stated. Working solutions wereprepared daily by proper dilution of the stock solutionswith ultra-pure water. All solutions were stored at 4 °C indark.

Apparatus

Chromatographic separations were performed with a 1200Binary SL Rapid Resolution series pump (Agilent, www.agilent.com). An Agilent Eclipse XDBC8 column(4.6 mm×150 mm, 5 μm particle size) was held at 30 °Cin an Agilent 1200 series SL column compartment. Asample volume of 10 μL was injected with an Agilent 1200series SL autosampler using a binary mobile phasecomposed of 20% water (containing 10 mmol L−1

ammonium acetate) and 80% methanol at a constant flowrate of 0.8 mL min−1. Mass spectrometry was performed onan Agilent 6410 triple-quadrupole mass spectrometer fittedwith an ESI MS source and controlled by a Mass Hunterworkstation. The ESI source conditions were established toobtain an average maximum intensity of the precursor ions.The nitrogen nebulizer pressure was set at 207 kPa and thenitrogen drying gas was set at 300 °C with a 10 L min−1

flow rate. The capillary voltage was set at 4000 V. ForMS/MS, N2 of high purity was used as a collision gas. Tooptimize the multiple reaction monitoring (MRM) tran-sitions, direct injection of each individual compound inmethanol was used. Optimum conditions are summarizedin Table 1.

146 R.-S. Zhao et al.

Ionic liquid/ionic liquid dispersive liquid-liquidmicroextraction

A 5.0 mL water sample was placed in a 10-mL test tubewith a conical bottom. A hydrophilic ionic liquid asdisperser solvent containing hydrophobic ionic liquid(extraction solvent) was rapidly injected into the samplesolution. The mixture of hydrophilic ionic liquid andhydrophobic ionic liquid was prepared immediately beforeuse. A cloudy water–hydrophilic ionic liquid–hydrophobicionic liquid mixture was formed in the test tube. Themixture was shaken and then centrifuged for 6 min at5,000 rpm, when the dispersed fine droplets of theextraction phase settled to the bottom of the conical testtube. The upper aqueous phase was removed with asyringe, the residue was dissolved in 50 μL methanol, and10 μL was injected with an Agilent 1200 autosampler forthe analysis.

Water samples

Four local environmental water samples, including lakewater, tap water, snow water and river water, were collectedfor validating the method. Lake water was obtained fromDaming Lake (Jinan, China). Rain water was obtained fromour lab. And snow samples was collected from ShandongAcademy of Sciences (Jinan, China). And river watersample was collected from Yellow river (Jinan, China). Allthe environmental water samples were stored in the coolplace avoiding light, and were filtered through 0.45 μmmicropore membranes before use.

Results and discussion

In order to obtain better extraction performance in IL/IL-DLLME, relative peak area (RPA) was used and defined asthe ratio between the peak area of the analyte (PA) and itsmaximal peak area (PA max) in the optimization. Relatedfactors that may affect the enrichment efficiencies, such astype and volume of hydrophobic ionic liquid (extractionsolvent), type and volume of hydrophilic ionic liquid(disperser solvent), extraction time, and NaCl content, wereinvestigated and optimized in detail.

Influence of type and volume of hydrophobic ionic liquid

For IL/IL-DLLME process, a suitable extraction solventhydrophobic ionic liquid is a major factor and should meetrequirements such as good chromatographic behavior, goodextraction properties and so on. Based on these consid-erations and previous studies [4, 6], three inexpensiveimidazolium-ILs [C4MIM][PF6], [C6MIM][PF6] and[C8MIM][PF6] are used. Experimental results in Fig. 1indicated that using ionic liquid [C8MIM][PF6] as extrac-tion solvent in IL/IL-DLLME procedure could achieveexcellent enrichment of TCS and TCC from aqueoussolutions. Therefore, [C8MIM][PF6] was selected as theextraction solvent in further work.

The volume of hydrophobic ionic liquid is an importantparameter affecting the extraction performance of IL/IL-DLLME. We describe here that the influence of [C8MIM][PF6] volume was investigated over the range 40–80 μL.The experimental results are shown in Fig. 2. According toFig. 2, the extraction efficiencies of TCS and TCC almostkept constant with increasing [C8MIM][PF6] volumebetween 40 and 50 μL. When the [C8MIM][PF6] volumewas more than 50 μL, the extraction efficiencies of TCCand TCS decreased. Therefore, 50 μL [C8MIM][PF6] wasused in all subsequent experiments.

0

20

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60

80

100

120

[C4MIM][PF6] [C6MIM][PF6] [C8MIM][PF6]

Rel

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TCC TCS

Fig. 1 Influence of the type of hydrophobic ionic liquid. Extractionconditions: sample volume, 5.0 mL; spiked concentration, 4.0 μg L−1

TCC and 20 μg L−1 TCS; [C4MIM][BF4] volume, 300 μL; volume ofsettled phase, 50±3 μL; pH 6; extraction time, 5 min

Table 1 Multiple reaction monitoring conditions for TCC and TCS

Compound Time(min) Div. valve Prec. ion Prod. ion (P1/P2) Frag. (V) Collision energy E1/E2 (V) ESI mode

0 To waste 314.9 162/126 90 8/16 Negative

TCC 4.5 To MS 314.9 162/126 90 8/16 Negative

TCS 5.6 To MS 286.8 286.8/35 70 0/0 Negative

Ionic liquid/ionic liquid dispersive liquid-liquid microextraction of triclosan and triclocarban 147

Influence of type and volume of hydrophilic ionic liquid

In IL/IL-DLLME, hydrophilic ionic liquids that aremiscible in hydrophobic ionic liquid and aqueous solutioncan be selected as disperser solvents [18]. These hydro-philic ionic liquids can disperse hydrophobic ionic liquid asvery fine droplets in aqueous solution. We described here,three hydrophilic ionic liquids with this ability, [EMIM][BF4], [C4MIM][BF4] and [C4MIM]NO3 were selected asdisperser solvent. And the influence of these solvents on theextraction performance of IL/IL-DLLME was investigated.A series of experiments was designed by using 300 μL ofeach disperser solvent containing 50 μL [C8MIM][PF6].Experimental results are shown in Fig. 3. From Fig. 3, it isobvious that extraction efficiencies with [C4MIM][BF4] and[C4MIM]NO3 were almost equal. Thus, [C4MIM][BF4] waschosen among these ionic liquids because of its higherextraction efficiencies and lower cost.

The next step was to optimize the [C4MIM][BF4]volume. Theoretically, at low [C4MIM][BF4] volume,[C4MIM][BF4] cannot disperse extraction solvent[C8MIM][PF6] properly and cloudy solution is not formedcompletely and at high volume, the solubility of TCC andTCS in water increases, therefore, the extraction efficien-cies decreases, too [18]. In order to obtain optimized[C4MIM][BF4] volume, it was investigated in the range of100–500 μL. Experimental results indicated that [C4MIM][BF4] volume in the range of 100–500 μL had no obviousinfluence on the extraction efficiencies of TCC and TCS.Therefore, 300 μL of [C4MIM][BF4] was selected in thefollowing experiments.

Influence of NaCl content

In order to investigate the influence of NaCl content onextraction efficiencies of TCC and TCS, a series of experi-ments was designed and performed by adding NaCl (0–20%,w/v) into the aqueous solutions. The results in Fig. 4 indicatedthat the extraction efficiencies of TCC and TCS decreasedwith the increase of NaCl content ranging from 0% to 20%.This behavior was also observed by Psillakis [19] andLópez-Blanco [20] in using LPME technique. Theyexplained that NaCl dissolved in water might have changedthe physical properties of the Nerst diffusion film and

0

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60

80

100

120

0 5 10 15 20

NaCl (%)

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Fig. 4 Influence of NaCl content. Extraction conditions: samplevolume, 5.0 mL; spiked concentration, 4.0 μg L−1 TCC and 20 μg L−1

TCS; [C8MIM][PF6] volume, 50 μL;[C4MIM][BF4], 300 μL; pH 6;extraction time, 5 min

Table 2 Linear range, limits of detection, and repeatability of themethod

Compounds Linear range(μg L−1)

R RSDs(n=7,%)

LODs(μg L−1)

TCC 0.5–100 0.9998 5.40 0.23

TCS 2.5–500 0.9988 6.41 0.35

0

20

40

60

80

100

120

[EMIM][BF4] [C4MIM][BF4] [C4MIM]NO3

Rel

ativ

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ak a

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TCC TCS

Fig. 3 Influence of the type of hydrophilic ionic liquid. Extractionconditions: sample volume, 5.0 mL; spiked concentration, 4.0 μg L−1

TCC and 20 μg L−1 TCS; [C8MIM][PF6] volume, 50 μL; volume ofdisperser solvent, 300 μL; pH 6; extraction time, 5 min

0

20

40

60

80

100

120

30 40 50 60 70 80 90

[C8MIM][PF6]volume (µL)

Rel

ativ

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ak a

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TCC TCS

Fig. 2 Influence of the volume of hydrophobic ionic liquid.Extraction conditions: sample volume, 5.0 mL; spiked concentration,4.0 μg L−1 TCC and 20 μg L−1 TCS; [C4MIM][BF4] volume, 300 μL;pH 6; extraction time, 5 min

148 R.-S. Zhao et al.

reduced the rate of diffusion of target analytes into theextraction solvent. On the basis of the above observations,no salt addition was performed in further experiments.

Influence of extraction time

The influence of extraction time on the extraction of TCCand TCS was examined in the range of 2.5–12.5 min.Experimental results shows that the relative peak areas ofTCC and TCS increased with extraction time in the rangeof 2.5–7.5 min, and then almost kept constant withextraction time in the range of 7.5–12.5 min. On the basisof these considerations, 7.5 min of extraction time wasadopted in further experiments.

Analytical performance

Under the above optimum conditions, linear range, limits ofdetection and repeatability were obtained (Table 2). Line-arity of the method was obtained over the range 0.5–100 μgL−1 for TCC and 2.5–500 μg L−1 for TCS, respectively.Based on a signal-to-noise (S/N) of 3, the limits ofdetection were 0.23–0.35 μg L−1, and similar to those ofconventional DLLME, IL-DLPME and TCIL-DLPMEtechniques [4, 7, 8] (Table 3). However, toxic solventswere used in conventional DLLME method [8]. Theheating and cooling steps in TCIL-DLPME may lead todegradation of some thermally unstable compounds or

other unexpected effects [7, 21]. A sensitive stir barsorptive extraction and liquid desorption-liquid chromatog-raphy–tandem mass spectrometry (SBSE-LD-LC-MS/MS)method has been developed for the determination of TCCin wastewater effluent [21], however, 22 h of extractiontime was too long. To assess the precision of themeasurement, the repeatability of the method was deter-mined by performing seven times using aqueous standardsolutions with 2.0 μg L−1 TCC and 10 μg L−1 TCS. Theywere 5.40% and 6.41% (RSDs, n=7) for TCC and TCS,respectively.

Real environmental water sample analysis

Four real environmental water samples, including tap water,river water, snow water and lake water samples obtainedlocally, were used to assess the applicability of the method.The experimental results (Table 4) indicated TCC and TCSwere not present in the four water samples. These sampleswere then spiked with TCC and TCS at different levels toinvestigate the effect of sample matrices. As can be seenfrom Table 4, the recoveries were in the range of 88%–111%. Compared with obvious DLLME, IL-DLPME,LPME, TCIL-DLPME [4–8], the recoveries were satisfac-tory. Typical chromatograms in real water samples aregiven in Fig. 5.

There are many reports on the contamination of TCCand TCS in environmental water samples. Li et al. found

Enrichment method Detection LODs (μg L−1) Liner range (μg L−1) Ref.

IL-DLPME HPLC-ESI-MS/MS 0.040–0.58 0.2–60 [4]

TCIL-DLPME HPLC-ESI-MS/MS 0.04–0.3 0.1–100 [7]

DLLME UHPLC-TUV 0.0421–0.134 0.025–100 [8]

SBSE-LD LC-MS/MS 0.001 — [22]

IL/IL-DLLME HPLC-ESI-MS/MS 0.23–0.35 0.5–500 This method

Table 3 Comparison of theanalytical methods for TCC andTCS with the present method

Table 4 Analytical results of real water samples

Sample Compounds Found (μg L−1) Spiked (μg L−1) Recovery (%) Spiked (μg L−1) Recovery (%)

Tap water TCC ND 1.00 106±4 4.00 98±7

TCS ND 5.00 103±4 20.0 94±9

Snow water TCC ND 1.00 111±4 4.00 94±5

TCS ND 5.00 105±5 20.0 92±5

River water TCC ND 1.00 102±2 4.00 93±3

TCS ND 5.00 99±5 20.0 88±4

Lake water TCC ND 1.00 101±4 4.00 96±5

TCS ND 5.00 109±9 20.0 98±7

ND not detected.

Ionic liquid/ionic liquid dispersive liquid-liquid microextraction of triclosan and triclocarban 149

2.08 μg L−1TCS in domestical water [8]. Schultz et al.reported that the concentration of TCC in wastewatereffluent ranged from 50 to 330 ng L−1 [22]. Cai et al.analyzed TCS in environmental water samples collectedfrom rivers and coastal water in Hong Kong, and itsconcentrations ranged from 4.1 to 117 ng L−1 [23]. Cooganet al. found 50–200 ng L−1 TCC, TCS, and methyl-TCS ina North Texas wastewater treatment plant receiving stream.From the above literatures, the method may be used for thedetermination of TCC and TCS in real-world watersamples, and its LODs could also be further improved fortheir sensitive determination by adding the sample volumeor in combination with SPE.

Conclusion

The purpose of this work was to investigate thefeasibility of a new IL/IL-DLLME system to enrichTCC and TCS in environmental water samples. This newextraction system avoided the use of toxic organicsolvents, and exhibited many merits such as rapidness,simplicity, easy to operate, and low consumption for theanalysis of TCC and TCS. The developed methodachieved wide linear range, good repeatability and lowlimits of detection for TCC and TCS. These factsdemonstrated that IL/IL-DLLME system was of greatpotential to be used for the enrichment and determinationof TCC and TCS in environmental water samples. It isexpected that IL/IL-DLLME may be a efficient extractionsystem for the analysis of other environmental pollutantsdue to its merits exhibited in this study.

Acknowledgments This work was financially supported by theNational Natural Science Foundation of China (21077069, 21007035),Natural Science Foundation of Shandong Province (ZR2010BL029),State Key Laboratory of Environmental Chemistry and Ecotoxicology,Research Center for Eco-Environmental Sciences, Chinese Academyof Sciences (KF2010-25).

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