Salting-out homogeneous liquid-liquid extraction in narrow-bore tube: Extraction and preconcentration of phthalate esters from water

J. Sep. Sci. 2013, 36, 939–946 939

Mir Ali FarajzadehSaheleh SheykhizadehParisa Khorram

Department of AnalyticalChemistry Faculty of Chemistry,University of Tabriz, Tabriz, Iran

Received September 2, 2012Revised November 21, 2012Accepted November 21, 2012

Research Article

Salting-out homogeneous liquid–liquidextraction in narrow-bore tube: Extractionand preconcentration of phthalate estersfrom water

In this study a simple and rapid sample preparation technique, homogeneous liquid–liquidextraction based on phase separation in the presence of a salt performed in a narrow-boretube, followed by GC-flame ionization detection has been developed. In this work, sodiumchloride and ACN were used as the salting-out agent and water-soluble extraction solvent,respectively. The homogeneous solution of water and ACN was broken by addition of thesalt. Small volume of ACN was collected on top of the tube and the extracted analytesin the collected phase were determined. It has been successfully used for the analysis offive phthalate esters as model compounds in aqueous sample. Experimental parametersaffecting the extraction efficiency such as kind and volume of the water-soluble organicsolvent, length and diameter of the tube, and pH of the sample solution were investigated.Under the optimal conditions, the LODs were between 0.02 and 0.7 �g/L and enrichmentfactors were in the range of 172–309. In addition, good linearity (between 1 and 5000 �g/L)and high precision on the base of RSD (<8%, C = 600 �g/L, n = 6) were achieved.

Keywords: GC / Homogeneous liquid–liquid extraction / Phthalate esters / SamplepreparationDOI 10.1002/jssc.201200834

1 Introduction

The sample preparation step in an analytical process typicallyinvolves extraction of target analytes from a sample matrix.The aim of this step is to clean up the matrices, isolate, and/orconcentrate the analytes of interest and render them in a formthat is compatible with analytical systems [1]. Traditional ex-traction methods such as liquid–liquid extraction and solidphase extraction are widely applied to determine componentsin environmental samples [2–7]. However, these conventionalpretreatment methods need either large quantities of sampleand organic solvent and are time-consuming. Also, the mate-rials used are expensive and not reusable [8]. To overcome thedisadvantages above, many analysts have paid great efforts.Solid-phase microextraction has been extensively investigatedto simplify sample treatment analysis of compounds [9–11].This method is solvent-free, simple, and fast. However, itsfiber is fragile, expensive, and it has limited lifetime. Alsosample carry-over can be a problem [12, 13]. Liquid-phasemicroextraction (LPME) has been developed as an alterna-tive extraction technique [14–16]. Single-drop microextrac-

Correspondence: Dr. Mir Ali Farajzadeh, Department of AnalyticalChemistry, Faculty of Chemistry, University of Tabriz, Tabriz, IranE-mail: [email protected]; [email protected]: +98 411 3340191

Abbreviations: EF, enrichment factor; FID, flame ionizationdetection; HLLE, homogeneous liquid–liquid extraction; PE,phthalate ester

tion and hollow fiber-LPME (HF-LPME) are two commonLPME techniques, which are inexpensive and there is consid-erable freedom in selecting appropriate solvents for extractionof different analytes. Since very little solvent is used, thereis minimal exposure to toxic organic solvent for the opera-tor [17]. However, these methods have some disadvantages:fast stirring would tend to form air bubble [18], extractionis time-consuming, and equilibrium could not be attainedafter a long time in most cases [19]. Another extraction proce-dure, namely homogeneous liquid–liquid extraction (HLLE),utilizes a phase separation phenomenon in a homogeneoussolution and a very small collected phase is resulted. In HLLE,the initial solution is homogeneous, namely, there is no in-terface between the water phase and water-miscible organicphase or between the water phase and water-immiscible or-ganic phase. In other words, the initial surface area of theinterface is infinitely large. Accordingly, no vigorous mechan-ical shaking is necessary [20, 21]. Generally, HLLE has beendone through binary and ternary component miscible sol-vent systems [22]. In these cases, phase separation is basedon salting-out phenomenon (with a salt or with an auxiliarysolvent) [23–29], temperature [30], pH [31,32], or ion-pair for-mation [33]. In the HLLE based on salting out, the mixture ofwater-soluble organic solvent and water can form two clearlyseparated phases in the presence of a salt and simultaneouslythe hydrophobic solutes are extracted into the separated or-ganic phase [34]. ACN, acetone, and isopropanol are commonextractants in this case [35]. The key points of developing apreprocessing method of HLLE include organic extractant

C© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.jss-journal.com

940 M. A. Farajzadeh et al. J. Sep. Sci. 2013, 36, 939–946

selection, salting-out reagent selection, and optimization oftheir ratio [25]. HLLE based on salting out has been utilized forthe extraction of some metals [36, 37], organic analytes [34],and pharmaceutical compounds [38, 39]. This method hasbeen developed as a sample preparation method due to itssimplicity, rapid partition equilibrium, and concentration ofanalytes in extract. Furthermore, the water-soluble organicsolvents used by this extraction technique are usually non-halogenated and nonaromatic solvents, and therefore thoughtto be more environmentally friendly than solvents such asbenzene, chloroform, and so on [34].

1,2-Benzenedicarboxylic acid esters, which are commonlydenoted as phthalate esters (PEs), are well-known polymeradditives used in formulations of cosmetics, paint, poly(vinylchloride) plastics, etc. However, their most important useis as plasticizers. PEs improve flexibility, workability, andgeneral handling properties only through weak secondarymolecular interactions with polymer chains [40–42]. It is es-timated that the production of these compounds in the worldis several million tons per year [43]. Being not covalentlybound to plastics, their migration from plasticized productsinto the environmental compartments and food and bever-ages may occur during their production, manufacture, use,and disposal [44]. Certain PEs and/or their metabolites havebeen shown carcinogenic, estrogenic, and endocrine disrup-tion activity [45–47]. Due to their potential risk for humanand animals’ health, several of them have been included inthe priority list of pollutants of different national and supra-national organizations. For example, the US EnvironmentalProtection Agency has established a maximum admissibleconcentration value of 6 �g/L for di-(2-ethylhexyl) phthalatein water [48]. Determination of PEs is not easy task. In fact thewidespread presence of PEs in the laboratory environment in-cluding air, glassware, and reagents can produce false positiveoutputs [49].

The aim of the present study was to investigate the feasi-bility of HLLE in a narrow-bore tube to extract and determinePEs in real aqueous samples. In this method, the phase sep-aration was performed based on salting-out phenomenon,and analytes were extracted into the fine droplets of extrac-tion solvent (ACN) collected on the surface of aqueous phase.The enriched analytes in the gathered organic phase weredetermined by GC-flame ionization detection (GC-FID). Af-ter optimization of parameters affecting the extraction, theexperimental results showed that this technique had fairlygood extraction potentials for some organic compounds suchas PEs.

2 Experimental

2.1 Reagents and solutions

The compounds studied were di-methyl phthalate, di-ethylphthalate, di-n-butyl phthalate (DNBP), di-isobutyl phthalate(DIBP), and di-(2-ethylhexyl) phthalate (DEHP). All PEs werepurchased from Sigma-Aldrich (St. Louis, MO, USA). ACN,

methanol, and acetone tested as the extraction solvent forthe extraction of analytes from water samples, were obtainedfrom Merck (Darmstadt, Germany). The HPLC-grade water(Caledon, Canada) was used for preparation of standard so-lutions and dilution of beverage and vinegar samples. High-purity sodium chloride and sodium hydroxide available fromMerck was used. A stock solution of the studied compoundswas prepared by dissolving five PEs in ACN to obtain a2500 mg/L solution and stored in a refrigerator. Standardsolution containing 250 mg/L of each PE in ACN was in-jected daily into the separation system (three times) so thatthe system quality could be evaluated (repeatability and re-sponse of detector for daily peaks areas were considered). Theobtained peaks areas were used in calculation of enrichmentfactors (EFs) and extraction recoveries (ERs) as it has beenexplained in Section 2.5, and determination of extraction sol-vent drop volume after extraction as it has been explained inSection 3.5.

2.2 Real samples

Mineral water, beverage (Coca cola), and vinegar were pur-chased from local supermarkets and sodium chloride 0.9%and dextrose 5% injectable solutions purchased from a drug-store to be tested as real samples. All samples had been packedin polymeric packages. Beverage and vinegar were dilutedwith HPLC-grade water at a ratio of 1:4 and the pH was ad-justed to 6–8 by sodium hydroxide solution. The pH of othersamples was within the range of 6–8.

2.3 Apparatus

Separation and determination of the selected PEs were car-ried out on a gas chromatograph (GC-15A, Shimadzu, Japan)equipped with a split/splitless injector and an FID. Purehelium (99.999%, Gulf Cryo, United Arab Emirates) at aconstant linear velocity of 30 cm/s was used as the carriergas. Injections (1 �L) were carried out in the splitless/splitmode with a 1 min purge time and split ratio of 1:10. Injec-tor temperature was 300�C. Chromatographic separation wasachieved on a semipolar SPB-5 capillary column (5% phenyl,95% methyl siloxane, 30 m × 0.25 mm id, and film thick-ness of 0.25 �m) (Supelco, Bellefonte, USA). Samples wereanalyzed using the following oven temperature program-ming: initial temperature 90�C (held for 2 min), increased by20�C/min to 190�C, then increased by 10�C/min to 290�Cand held at 290�C for 4 min. The total time for one GCrun was 21 min. The FID temperature was maintained at300�C. Hydrogen gas was generated with a hydrogen gener-ator (OPGU-1500S, Shimadzu, Japan) for FID at a flow rateof 30 mL/min. The flow rate of air for FID was 300 mL/min.GC-MS analysis was carried out on an Agilent 6890N gas chro-matograph with a 5973 mass-selective detector (Agilent Tech-nologies, CA, USA). The separation was carried out on anHP-5 MS capillary column (equivalent to SP-5 capillary


J. Sep. Sci. 2013, 36, 939–946 Sample Preparation 941

Figure 1. Scheme of salting-out homogeneous liquid–liquid extraction procedure. (A) A narrow-bore tube filled with the mixture of ACNand aqueous solution of analytes; (B) formation of cloudy solution after addition of sodium chloride; and (C) removal of a portion ofextractant (ACN) by a capillary tube after ultrasonication in order to inject into the GC-FID.

column) (30 m × 0.25 mm id, and film thickness of 0.25�m, Hewlett-Packard, Santa Clara, USA). Helium was usedas the carrier gas at a flow rate of 1.0 mL/min. The oventemperature programming was the same as GC-FID analy-sis mentioned above. The Hettich centrifuge, model D-7200(Kirchlengern, Germany), was used for accelerating phaseseparation.

2.4 HLLE procedure

The set-up included a narrow-bore glass tube (100 cm × 5 mmid). One end of the tube was closed with a septum. Initially in-ner wall of the narrow-bore tube was cleaned by filling it with3 M sodium hydroxide solution. After 30 min it was rinsedthoroughly with de-ionized water. This prevents fine dropletsof extraction solvent from adhering to the inner wall of thetube during extraction. A homogeneous standard solution orsample solution containing 17.3% v/v ACN as extraction sol-vent was prepared. Then, by using a 20-mL syringe 18 mLof the prepared solution was filled into the tube. NaCl wasgrained manually in a mortar and 5.4 g of it was added to thesolution. During this step many fine droplets of ACN wereformed. The tube was sonicated (Zyklusmed, Germany) for5 min. By this action, almost all of the fine droplets reachedtop of the tube and floated on the surface of aqueous phase asa separate layer due to lower density of ACN than water. Dur-ing this step, analytes were extracted into the fine droplets.The volume of the separated phase was about 23 ± 2 �L. Fi-nally, a portion of the gathered organic phase containing thetarget analytes was easily transferred by a capillary tube (glasscapillary tube, 100 mm length and 1.5 mm od, Electrother-

mal, Denmark); 1 �L of the collected phase was injected intothe GC-FID for analysis. The extraction procedure is shownas a scheme in Fig. 1.

2.5 Analytical parameters

In order to evaluate performance of the proposed proce-dure two parameters, EF and ER, were employed. EF is de-fined as the ratio of the analyte concentration in the col-lected phase (Ccoll) to its initial concentration (Co) within thesample:

EF = Ccoll/Co (1)

ER is defined as the percentage of the total analyte amount(no), which was extracted into the collected phase (ncoll):

ER = (ncoll/no) × 100 = [(Ccoll×Vcoll)/(Co×Vaq)] × 100

ER = (Vcoll/Vaq) × EF × 100 (2)

where Vcoll and Vaq are the volumes of collected phase andaqueous solution, respectively. It should be noted that re-moval of the whole organic phase collected on the aqueousphase into the narrow-bore tube is difficult. To calculate vol-ume of the collected phase, the method was performed ona blank solution under the optimized conditions, then 5 �L(Vadded) of 250 mg/L standard solution of PEs in ACN wasadded into organic phase collected on top of the tube (seeSection 3.5)



3 Results and discussion

In this study, HLLE combined with GC-FID was used forpreconcentration and determination of five PEs in aqueoussamples. In order to obtain high recoveries and EFs, variousparameters such as kind and volume of extraction solvent,sample volume, etc. were optimized.

3.1 Effect of water-miscible organic solvent nature

The criteria of solvent selection in this technique were lowerdensity than water, high extraction capability, and beingenvironmentally friendly. Accordingly, ACN, acetone, andmethanol were chosen and tested. The experimental resultsrevealed that among the solvents tested ACN can be quicklyseparated, while other solvents cannot be separated fromwater after addition of 30% w/v NaCl as a phase separatorreagent. Thus, ACN was selected as the extraction solvent.Experiments showed that phase separation can be achievedat less than 20% v/v of ACN in water.

3.2 Effect of the initial volume of ACN

The selection of extraction solvent volume depends on sol-vent gathering ability on the aqueous phase after extraction,repeatability of results, and extraction efficiency. The influ-ence of extraction solvent volume on the extraction efficiencyof PEs was studied in the range 17.0–19.6% v/v. The volumeof the gathered phase increased by increasing the volume ofACN. But another factor, i.e. dilution, caused EFs (analyticalsignals) to be decreased at high volumes of extractant. On theother hand, at less than 17.3% v/v of acetonitril phase sepa-ration was not accomplished or the gathered organic phasevolume was too low to be collected by the capillary tube. There-

Table 1. Quantitative features of the proposed method for theselected PEs

Analyte LR R2b) LOD LOQ RSD%e) EF ± SDf)

(�g/L)a) (�g/L)c) (�g/L)d)

Di-methylphthalate

10–5000 0.999 0.7 2 5 172 ± 9.0

Di-ethylphthalate

2.0–5000 0.998 0.7 2 3 247 ± 8.0

DIBP 1.0–5000 0.995 0.02 0.05 4 305 ± 16DNBP 1.0–5000 0.996 0.1 0.5 5 309 ± 15DEHP 1.0–5000 0.994 0.02 0.06 8 308 ± 24

a) Linear range.b) Square of correlation coefficient.c) Limit of detection, S/N = 3.d) Limit of quantitation, S/N = 10.e) Relative standard deviation (600 �g/L, n = 6).f) Mean enrichment factor ± standard deviation, n = 3.

Figure 2. GC-FID chromatograms of (A) unspiked vinegar,(B) spiked vinegar with 500 �g/L of each PE, and (C) standard so-lution of PEs in the ACN (250 mg/L of each PE). In chromatograms(A) and (B), the preconcentration technique under the optimizedconditions was performed on samples and 1 �L of the collectedorganic phase was injected into GC. In the case of chromatogram(C), 1 �L was directly injected into the separation system. Peaksidentification: 1, di-methyl phthalate; 2, di-ethyl phthalate; 3, DIBP;4, DNBP; and 5, DEHP.

fore, 17.3% v/v of ACN was used as the optimal volume forthe HLLE of PEs.

3.3 Effect of pH

pH value of solution is important as it affects the hydrolysisstatus as well as solubility of the analytes. The effect of pH onthe extraction efficiency was examined in pH range 2–12. Thequantitative extraction was obtained at pH 6–8. Decreasingin extraction efficiency of PEs is due to hydrolysis of them inacidic or basic conditions. In this study, except beverage andvinegar, pH of all samples was between 6 and 8. Therefore,pH of beverage and vinegar after dilution was adjusted in therange 6–8.

3.4 Optimization of the sample volume

The effect of sample size on the extraction efficiency wasinvestigated using three tubes having different volumes (12,18, and 43 mL); two tubes with different lengths (70 and100 cm) and a constant id (5 mm); and one tube with lengthof 100 cm length and id of 7 mm. Increasing sample volumeled to increase of the analytical signals. But in the case of thetube with 7 mm id (43 mL), removal of organic phase collectedon the surface of aqueous sample was difficult. Therefore, the



Figure 3. Total ion chromatograms (TIC) of (A) vinegar, and (B) blank, after performing the proposed method, and mass spectra of (C) scan573 (retention time 10.26), (D) DIBP, (E) scan 626 (retention time 11.02 min), (F) DNBP, (G) scan 952 (retention time 15.68 min), and (H) DEHP.

tube with dimensions 100 cm × 5 mm id and a capacity of18 mL was selected for the following experiments.

3.5 Determination of collected organic phase volume

after extraction

To determine the volume of collected organic phase on thesurface of aqueous sample after extraction, a blank solution(17.3% v/v ACN in water) was prepared and phase separationperformed by adding 30% w/v NaCl. Then 5 �L (Vadded) of

250 mg/L standard solution of PEs in ACN was added tothe collected organic phase on top of the tube and 1 �L ofit injected into the separation system. In order to determinethe volume of extraction solvent (Vcoll) after extraction, thefollowing equation was used:

Vcoll= ((Adir/Aext)×Vadded) − 5 (3)

where Adir is the peak area of each PE after direct injection of1 �L of their standard solution (250 mg/L in ACN) into GC.Aext is the peak area of each PE in the obtained chromatogramafter addition of their standard solution into collected ACN on



Table 2. Study of matrix effect in samples spiked at different concentrations; analytes contents were subtracted from the found amounts

Mean recovery (%) ± SD (n = 3)

Analyte Mineral water Beveragea) Vinegara) NaCl 0.9% Dextrose 5%

All samples were spiked with each analyte at a concentration of 100 �g/L.Di-methyl phthalate 99.2 ± 4 68.2 ± 1 65.0 ± 4 102 ± 6 85.0 ± 7Di-ethyl phthalate 98.3 ± 3 67.3 ± 4 63.3 ± 3 89.2 ± 5 76.3 ± 7DIBP 88.0 ± 1 61.4 ± 1 66.1 ± 1 79.3 ± 2 65.4 ± 2DNBP 87.4 ± 2 64.3 ± 4 62.4 ± 3 66.2 ± 2 69.0 ± 5DEHP 96.1 ± 3 62.4 ± 4 61.0 ± 4 80.0 ± 5 70.2 ± 3All samples were spiked with each analyte at a concentration of 500 �g/L.Di-methyl phthalate 94.3 ± 1 110 ± 9 100 ± 5 107 ± 1 100 ± 1Di-ethyl phthalate 86.2 ± 2 94.2 ± 1 95.2 ± 1 96.3 ± 1 86.2 ± 2DIBP 85.0 ± 2 88.3 ± 7 85.0 ± 11 96.1 ± 5 80.3 ± 2DNBP 86.1 ± 7 99.0 ± 11 81.3 ± 10 94.3 ± 3 79.2 ± 1DEHP 93.2 ± 5 81.4 ± 5 82.4 ± 12 74.0 ± 1 73.3 ± 3All samples were spiked with each analyte at a concentration of 1000 �g/L.Di-methyl phthalate 93.0 ± 1 103 ± 8 96.4 ± 1 98.2 ± 2 86.3 ± 3Di-ethyl phthalate 91.3 ± 2 104 ± 5 74.0 ± 2 96.3 ± 5 83.1 ± 3DIBP 80.4 ± 1 98.3 ± 3 76.3 ± 4 93.4 ± 1 76.0 ± 1DNBP 92.0 ± 7 104 ± 4 80.0± 2 99.0 ± 2 74.3 ± 4DEHP 82.3 ± 7 107 ± 13 81.0 ± 2 104 ± 7 84.3 ± 3

a) Diluted with HPLC-grade water at a ratio of 1:4 and their pHs were adjusted to 6–8.

top of the tube. The collected phase volume after extractionwas 23 ± 2 �L.

3.6 Evaluation of the method performance

Under the optimum experimental conditions, the proposedmethod was applied to standard solutions of analytes in or-der to evaluate analytical characteristics of the method. Lin-ear ranges, squared correlation coefficients (R2), LODs, limitsof quantitation (LOQs), RSDs, and EFs were calculated andsummarized in Table 1. As given in this table, the calibrationcurves for PEs exhibit wide linear ranges with good linearties(R2 > 0.994). LODs and LOQs for the tested PEs were inthe range of 0.02–0.7 and 0.05–2 �g/L, respectively. Repeata-bility of the method was assessed by its application on thesix similar standard solutions at two concentrations (600 and1200 �g/L, for each PE) and RSDs were in the range of 3–8%. High EFs ranging from 172 to 309 were obtained. Theseresults indicate that HLLE combined with GC-FID can beused as alternative method for PEs extraction/determinationin aqueous samples.

3.7 Real sample analysis

The proposed HLLE method was applied to extraction anddetermination of PEs in different samples. For this purposea mineral water, a beverage, a vinegar, 0.9% sodium chlo-ride and 5% dextrose injectable solutions were tested as sam-ple. Typical GC-FID chromatograms of vinegar (before and

Table 3. PEs contents of the real aqueous samples

Analyte Mean concentration of PEs (�g/L) ± SD (n = 3)

Mineral Beverage Vinegar NaCl Dextrosewater 0.9% 5%

Di-methyl phthalate NDa) ND ND ND NDDi-ethyl phthalate ND ND ND ND NDDIBP 8.0 ± 1 35 ± 4 90 ± 7 ND NDDNBP 15 ± 1 18 ± 3 30 ± 6 12 ± 2 9.0 ± 1DEHP 20 ± 4 31 ± 4 79 ± 6 21 ± 4 39 ± 5

a) Not detected.

after spiking with 500 �g/L of each PE) after performingthe proposed method and direct injection of standard solu-tion are shown in Fig. 2. To identify the observed peaks inthe retention times of DIBP, DNBP, and DEHP in vinegarchromatogram, this sample (after performing the proposedmethod) was analyzed by GC-MS. By comparison of massdata for scans 573, 626 and 952 (retention times 10.26, 11.02and 15.68 min, respectively) with those of DIBP, DNBP andDEHP, the presence of these PEs was confirmed in the vine-gar sample (Fig. 3). In order to evaluate the matrix effect,mean recoveries of spiked samples with PEs at three lev-els (100, 500 and 1000 �g/L of each PE) were determinedand compared with those of standard solutions at the sameconcentrations (Table 2). The results suggest that mineralwater and injectable solutions matrices have little effect onHLLE efficiency and there is no need for their dilution or per-forming other treatments. But due to strong matrix effect in



Table 4. Comparison of the proposed method with the other methods used in PEs determination

Method LODa) (�g/L) LRb) (�g/L) RSDc) (%) Extraction Sample EFd) Ref.time (min) volume (mL)

Dynamic LPME-GC-FIDe) 0.43–4.30 5–5000 5.3–6.4 _ 22.5 28–95 [17]DLLME-HPLC-VWDf) 0.64–1.8 5–5000 4.3–5.9 5 5 44–196 [41]USE-SPME-GC-FIDg) 0.006–0.03 0.1–1000 5–9 40 _ _ [50]LPME-GC-MSh) 0.02–0.03 0.05–100 5.5–6.4 25 10 358–409 [42]HLLE in narrow-bore tube GC-FID 0.02–0.71 1–5000 3–8 10 18 172–309 This method

a) Limit of detection.b) Linear range.c) Relative standard deviation.d) Enrichment factor.e) Dynamic liquid-phase microextraction-GC-flame ionization detector.f) Dispersive liquid–liquid microextraction-HPLC-variable wavelength detector.g) Ultrasonic solvent extraction-solid-phase microextraction-GC-flame ionization detector.h) Liquid-phase microextraction based on the solidification of a floating organic microdrop-GC-MS.

beverage and vinegar samples, they were diluted with HPLC-grade water at a ratio of 1:4 before applying the method onthem. By this action matrix effect reduced considerably inthe mentioned samples in 500 and 1000 �g/L spiked levels.However significant matrix effects are observed at 100 �g/Lspiked level. In order to eliminate the matrix effect standardaddition method was employed in quantitation of analytes insamples. PEs content of solutions filled in polymeric pack-ages is shown in Table 3. Di-methyl phthalate and di-ethylphthalate were not detected in samples. On the other hand,DNBP and DEHP were determined in the range of 9–79 �g/Lin samples. DIBP was found in all samples, except 0.9% NaCland 5% dextrose injectable solutions.

3.8 Comparison of the proposed method with other

methods

In Table 4, LOD, linear range, RSD, extraction time, samplevolume, and EF of the proposed method were compared withthose of other methods for extraction and determination ofPEs in water samples. In the proposed method, LOD, linearrange, and RSD values are comparable or better than those ofother mentioned methods. The extraction time of the presentmethod relative to other methods is very short. EFs of presentmethod are better than EFs of other mentioned methods (ex-cept LPME-GC-MS). By considering the results, this methodproved to be a rapid, sensitive, efficient, reliable, and simpletechnique in the extraction and preconcentration of PEs fromaqueous samples and can be extended to other applications.

4 Conclusions

In the presented study a simple and fast salting-out HLLEmethod performed in a narrow-bore tube was developed andapplied for extraction of PEs in water samples. Comparedwith other conventional sample preparation methods, the

proposed technique offers advantages such as relatively shortanalysis time, and high EFs. The results obtained from val-idation indicate that the proposed method can be used fordetermination of PEs in water samples.

The authors thank the Research Council of Tabriz Universityfor the financial support.

The authors have declared no conflict of interest.

5 References

[1] Smith, R. M., J. Chromatogr. A 2003, 1000, 3–27.

[2] Przyjazny, A., Kokosa, J. M., J. Chromatogr. A 2002, 977,143–153.

[3] Dean, J. R., Extraction Methods for Environmental Anal-ysis, John Wiley & Sons, Chichester, UK 1998.

[4] David, F., Sandra, P., Tienpont, B., Vanwalleghem, F., in:Staples, C. A. (Ed.), The Handbook of EnvironmentalChemistry, Vol. 3, Springer, Berlin 2003, p. 9.

[5] He, Y., Lee, H. K., Anal. Chem. 1997, 69, 4634–4640.

[6] Wang, W. D., Huang, Y. M., Shu, W. Q., Cao, J., J. Chro-matogr. A 2007, 1173, 27–36.

[7] Jara, S., Lysebo, C., Greibrokk, T., Lundanes, E., Anal.Chim. Acta 2000, 407, 165–171.

[8] Zhou, J., Zeng, Z., Anal. Chim. Acta 2006, 556, 400–406.

[9] Jinno, K., Kawazoe, M., Saito, Y., Takeichi, T., Hayashida,M., Electrophoresis 2001, 22, 3785–3790.

[10] Prokupkova, G., Holadava, K., Poustka, J., Hajslova, J.,Anal. Chim. Acta 2002, 457, 211–223.

[11] Zeng, Z. R., Qiu, W. L., Huang, Z. F., Anal. Chem. 2001,73, 2429–2436.

[12] Djozan, Dj., Assadi, Y., Hosseinzadeh Haddadi, S., Anal.Chem. 2001, 73, 4054–4058.

[13] Djozan, Dj., Assadi, Y., Chromatographia 2004, 60,313–317.

[14] Batlle, R., Nerın, C., J. Chromatogr. A 2004, 1045,29–35.



[15] Psillakis, E., Kalogerakis, N., Trends Anal. Chem. 2003,22, 565–574.

[16] Pedersen-Bjergaard, S., Rasmussen, K. E., Anal. Chem.1999, 71, 2650–2656.

[17] Xu, J., Liang, P., Zhang, T., Anal. Chim. Acta 2007, 597,1–5.

[18] Shen, G., Lee, H. K., Anal. Chem. 2002, 74, 648–654.

[19] Ahmadi, F., Assadi, Y., Hosseini, M. R. M., Rezaee, M., J.Chromatogr. A 2006, 1101, 307–312.

[20] Rezaee, M., Assadi, Y., Hosseini, M. R. M., Aghaee, E.,Ahmadi, F., Berijani, S., J. Chromatogr. A 2006, 1116,1–9.

[21] Ghiasvand, A. R., Shadabi, S., Mohagheghzadeh, E.,Hashemi, P., Talanta 2005, 66, 912–916.

[22] Anthemidis, A. N., Ioannou, K. I. G., Talanta 2009, 80,413–421.

[23] Razmara, R. S., Daneshfar, A., Sahrai, R., J. Ind. Eng.Chem. 2011, 17, 533–536.

[24] Wang, X., Zhao, X., Liu, X., Li, Y., Fu, L., Hu, J., Huanga,C., Anal. Chim. Acta 2008, 620, 162–169.

[25] Zhao, F. J., Tang, H., Zhang, Q. H., Yang, J., Davey, K.,Wang, J. P., J. Chromatogr. B 2012, 881, 119–125.

[26] Gupta, M., Pillai, A. K. K. V., Singh, A., Jain, A., Verma,K. K., Food Chem. 2011, 124, 1741–1746.

[27] Myasein, F., Kim, E., Zhang, J., Wu, H., El-Shourbagy, T.A., Anal. Chim. Acta 2009, 651, 112–116.

[28] Ebrahimzadeh, H., Yamini, Y., Kamarei, F., Shariati, S.,Anal. Chim. Acta 2007, 594, 93–100.

[29] Tavakoli, L., Yamini, Y., Ebrahimzadeh, H., Shariati, S., J.Chromatogr. A 2008, 1196, 133–138.

[30] Murata, K., Yokoyama, Y., Ikeda, S., Anal. Chem. 1972,44, 805–810.

[31] Takahashi, A., Yamaguchi, H., Igarashi, S., Bunseki Ka-gaku 1997, 46, 55–58.

[32] Farajzadeh, M. A., Bahram, M., Zorita, S., GhorbaniMehr, S., J. Hazard. Mater. 2009, 161, 1535–1543.

[33] Sudo, T., Igarashi, S., Talanta 1996, 46, 233–237.

[34] Cai, Y., Cail, Y., Shi, Y., Liu, J., Mou, S., Lu, Y., Microchim.Acta 2007, 157, 73–79.

[35] Liu, J., Jiang, M., Li, G., Xu, L., Xie, M., Anal. Chim. Acta2010, 679, 74–80.

[36] Nagaosa, Y., Sakata, K., Talanta 1998, 46, 647–654.

[37] Chung, N. H., Tabata, M., Talanta 2002, 58, 927–933.

[38] Zhang, J., Wu, H., Kim, E., El-Shourbagy, T. A., Biomed.Chromatogr. 2009, 23, 419–425.

[39] Rodila, R. C., Kim, J. C., Ji, Q. C., El-Shourbagy,T. A., Rapid Commun. Mass Spectrom. 2006, 20,3067–3075.

[40] Lopez-Jimenez, F. J., Rubio, S., Perez-Bendito, D., Anal.Chim. Acta 2005, 551, 142–149.

[41] Liang, P., Xu, J., Li, Q., Anal. Chim. Acta 2008, 609, 53–58.

[42] Farahani, H., Ganjali, M. R., Dinarvand, R., Norouzi, P.,Talanta 2008, 76, 718–723.

[43] Polo, M., Llompart, M., Garcia-Jares, C., Cela, R., J. Chro-matogr. A 2005, 1072, 63–72.

[44] Balafas, D., Shaw, K. J., Whitfield, F. B., Food Chem. 1999,65, 279–287.

[45] Harrison, P. T. C., Holmes, P., Humfrey, C. D. N., Sci. TotalEnviron. 1997, 205, 97–106.

[46] Gray, L. E., Ostby, J., Furr, J., Veeramachaneni, D. N. R.,Parks, L., Toxicol. Sci. 2000, 58, 350–365.

[47] Heudorf, U., Mersch-Sundermannb, V., Angerer, J., Int.J. Hyg. Environ. Health 2007, 210, 623–634.

[48] National Primary Drinking Water Regulations, Fed-eral register, Part 12, 40 CFR Part 141, US Envi-ronmental Protection Agency, Washington, DC 1991,p. 395.

[49] Del Carlo, M., Pepe, A., Sacchetti, G., Compagnone,D., Mastrocola, D., Cichelli, A., Food Chem. 2008, 111,771–777.

[50] Li, X., Zeng, Z., Chen, Y., Xu, Y., Talanta 2004, 63,1013–1019.


Documents

Salting-out homogeneous liquid-liquid extraction in narrow-bore tube: Extraction and preconcentration of phthalate esters from water