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Robust Ionic Liquid–Based DispersiveLiquid–Liquid Microextraction Method forDetermination of Chromium(VI) in SalineSolutionsMohsen Taziki a , Farzaneh Shemirani a & Behrooz Majidi ba School of Analytical Chemistry, University College of Science ,University of Tehran , Tehran , Iranb Department of Chemistry, Faculty of Sciences , Mahabad Branch,Islamic Azad University , Mahabad , IranAccepted author version posted online: 01 Oct 2013.Publishedonline: 02 Dec 2013.

To cite this article: Mohsen Taziki , Farzaneh Shemirani & Behrooz Majidi (2013) Robust IonicLiquid–Based Dispersive Liquid–Liquid Microextraction Method for Determination of Chromium(VI)in Saline Solutions, Communications in Soil Science and Plant Analysis, 44:22, 3400-3411, DOI:10.1080/00103624.2013.847452

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Communications in Soil Science and Plant Analysis, 44:3400–3411, 2013Copyright © Taylor & Francis Group, LLCISSN: 0010-3624 print / 1532-2416 onlineDOI: 10.1080/00103624.2013.847452

Robust Ionic Liquid–Based DispersiveLiquid–Liquid Microextraction Method for

Determination of Chromium(VI) in Saline Solutions

MOHSEN TAZIKI,1 FARZANEH SHEMIRANI,1

AND BEHROOZ MAJIDI2

1School of Analytical Chemistry, University College of Science, University ofTehran, Tehran, Iran2Department of Chemistry, Faculty of Sciences, Mahabad Branch, Islamic AzadUniversity, Mahabad, Iran

Robust ionic liquid–based dispersive liquid–liquid microextraction (IL-DLLME) is afast and simple method for extraction and preconcentration of metal ions from sampleswith high salt content. This method can solve the problems associated with the lim-ited application of the conventional IL-DLLME in these samples. In this procedure, thehydrophobic chelate of chromium with ammonium pyrrolidinedithiocarbamate (APDC)was extracted into the fine droplets of 1-hexyl-3-methylimidazolium hexafluorophos-phate ([Hmim][PF6]), which was dispersed into the aqueous sample solution. Severalfactors that influence the microextraction efficiency were investigated. In optimum con-ditions a linear calibration graph in the range of 0.5–70 µg L−1 of Cr in the initialsolution with r = 0.9998 was obtained. Detection limit was 0.16 µg L−1 and relativestandard deviation (RSD) for 20 µg L−1 of Cr was 2.68% (n = 10), respectively. Theproposed method was successfully applied for the determination of Cr(VI) in watersamples and food additives.

Keywords Chromium(VI), ionic liquid–based dispersive liquid–liquidmicroextraction, microsample, saline sample

Introduction

Chromium (Cr) is a major pollutant of the environment, usually a result of some industrialpollution including steel works, industrial electroplating, wood preservation, and artificialfertilizers (Liang and Sang 2008; Kotas and Stasicka 2000). Chromium(III) and Cr(VI)are two stable oxidation states of Cr in natural water (Narayana et al. 2010) and have dif-ferent toxicities, motilities, and bioavailabilities. Chromium(VI) is known to be toxic toboth plants and animals as well as potentially being carcinogenic, whereas Cr(III) is essen-tial to human glucidic metabolism and exhibits much less toxicity and mobility (Myerset al. 2000; Zhitkovich et al. 2002). The World Health Organization (WHO) thought thatthe guideline value of 0.05 mg L−1 of Cr(VI) was too high (Kiran et al. 2008), comparedwith its high risk of carcinogenicity. Consequently, the development of a sensitive method,as well as the determination method of Cr in the environment is absolutely required.

Received 25 July 2011; accepted 9 July 2012.Address correspondence to Farzaneh Shemirani, School of Analytical Chemistry, University

College of Science, University of Tehran, Tehran, Iran. E-mail: shemiran@khayam.ut.ac.ir

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Chromium(VI) in Saline Solutions 3401

For this purpose, various separation and preconcentration methods, such as on liquid–liquid extraction (LLE) (Wang et al. 2000; Beni, Karosi, and Posta 2007), solid-phaseextraction (SPE) (Maltez and Carasek 2005; Narin, Kars, and Soylak 2008; Pramanik,Dey, and Chattopadhyay 2007; Tuzen and Soylak 2007), coprecipitation (Karatepe et al.2010; Krishna et al. 2004), etc. However, the disadvantages, such as long time frame, unsat-isfactory enrichment factors, and large volume of organic solvents and secondary waste,limit their applications. Ion chromatography (Paquet et al. 1998), cloud-point extraction(CPE) (Yeh and Jiang 2004), capillary electrophoresis (Ezoddin et al. 2010; Kuban andKuban 2003), and dispersive liquid–liquid microextraction (DLLME) (Chena et al. 2010)are fairly new methods of sample preparation for the separation and preconcentration ofCr and proven to be simple, inexpensive, fast, and virtually solvent-free sample pretreat-ment techniques with extensive applications. However, in the presence of high salt content,the performance of these pretreatment techniques significantly decreases. This loss of per-formance can occur because of slow mass transfer, increased wall effect, settlement orphase-separation failure, variation of the extractant phase volume, and residual salinityfrom matrix (Baghdadi and Shemirani 2009).

Room-temperature ionic liquids (RTILs) are being considered as replacement solventsin the sample preparation because of their unique chemical and physical properties such asnegligible vapor pressure, nonflammability, good extractability for various organic com-pounds and metal ions as neutral or charged complexes, as well as tunable viscosity andmiscibility with water and organic solvents (Gharehbaghi, Shemirani, and Farahani 2009).

The main advantages of DLLME are simplicity, rapidity, low cost, low sample vol-ume, high recovery and enrichment factor, and environmental benignity (Zang et al. 2009).Currently this technique mostly has been applied to water samples and an initial extrac-tion and/or further cleanup would be needed for samples with complex matrixes (Yaminiet al. 2010). In comparison with the conventional DLLME, ionic liquid–based DLLME(IL-based DLLME) uses ionic liquids instead of toxic organic liquids as the extractionsolvent. The IL-based DLLME has been frequently used for preconcentration of organicand inorganic compounds. However, the performance of the IL-based DLLME decreasessignificantly as the salt content of sample solution is increased (Yousefi and Shemirani2010). In the presence of salt, the solubility of ILs increases because of the increasein ionic strength of the aqueous solution. Therefore, the volume of the settled phase inIL-based DLLME depends strongly on the salt concentration of samples. Moreover, ILsdissolve completely at high concentration of salt and the cloudy solution is not formed.Consequently, IL-based DLLME cannot be applied for extraction and preconcentration ofanalyte from samples containing high salt concentration. The main aim of this article is tostudy the applicability of proposed IL-based DLLME followed by flame atomic absorp-tion (FAAS) equipped with a homemade microsample introduction system and an atomconcentrator tube to determine Cr in saline samples.

Materials and Methods

Instrumentation

A Varian model AA-400 atomic absorption spectrometer, equipped with a deuterium lampbackground and with Cr hollow cathode lamp, was used for the determination of Cr. Thelamp was operated at 4 mA, using the wavelength at 357.9 nm, slit of 0.5 nm, burner heightof 8 mm, and acetylene gas flow rate of 1.5 L min−1. All measurements were carried outin peak high mode (measurement time of 5 s). A Universal 320 R centrifuge equipped

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3402 M. Taziki, F. Shemirani, and B. Majidi

with a swing out rotor (12-place, 5000 rpm, cat. no. 1628A) was obtained from Hettich(Kirchlengern, Germany). A Metrohm digital pH meter (model 692, Herisau, Switzerland),equipped with a glass-combination electrode was used for pH adjustment. A homemademicrosample introduction system was used for aspiration of the extractant phase in flameatomic absorption spectrometry (Yousefi and Shemirani 2010; Khani, Shemirani, andMajidi 2011). Maximum peak height was measured as the absorbance signal.

Reagents and Solutions

All chemicals used in this work were of analytical grade of Merck (Merck, Darmstadt,Germany) or Aldrich (Aldrich Chemical Co., Milwauke, Wisc., USA). All aqueous solu-tions were prepared in double-distilled deionized water. All organic solvents (HPLC grade)were purchased from Aldrich. A stock standard solution of Cr(VI) at a concentration of1000 µg mL−1 was prepared by dissolving amounts of potassium dichromate (K2Cr2O7)in 100 mL of water. Working standard solutions were obtained by appropriate dilution ofthe stock standard solution. A solution of 200 mg mL−1 NaPF6 was prepared by dissolvingan appropriate amount of sodium hexafluorophosphate (NaPF6) in doubly distilled water.

To decrease the viscosity of ILs and facilitate sample handling, dilution with organicsolvent is necessary, so working solutions of 1-hexyl-3-methylimidazolium hexafluo-rophosphate [Hmim][PF6] were prepared in ethanol. Effect of [Hmim][PF6] was studied atvarious rates (60, 65, 70, 75, 80, 85, and 90 mg) in the presence of 1 mL NaPF6 (200 mgmL−1). Effect of volume of NaPF6 200 mg L−1 was investigated at various rates (100,300, 500, 700, 1000, and 1200 µL) in the presence of 75 mg [Hmim][PF6]. The formationof metal complex and its chemical stability are the two important factors influencing theextraction of metal ions, and the pH plays a unique role on metal-chelate formation andsubsequent extraction. Seven levels of pH (2, 3, 4, 5, 6, 7, and 8) on the extraction of Crfrom water samples were applied.

Ammonium pyrrolidinedithiocarbamate (APDC) reacts with Cr(VI) quickly at roomtemperature because it is easy to displace the Cr(VI)-coordinated water molecules inthe aqueous phase by the dithiocarbamate ligand (Chwastowska et al. 2005). A solutionof 0.02 mol L−1 of chelating agent, APDC, was prepared by dissolving an appropriateamount of this reagent in ethanol. The effect of concentration of APDC was investigatedat various rates (6.1 × 10−5, 1.2 × 10−4, 3.6 × 10−4, 0.6 × 10−3, 0.84 × 10−4, and 1.2 ×10−3 mol L−1).

The diluting agent must dissolve the IL and complex, completely. Acetone, methanol,and ethanol were examined in this work. In the presence of acetone and methanol, maxi-mum absorbance was obtained, but the IL phase could not be dissolved in 50 µL methanoland acetone, completely. In the presence of ethanol, the sample was clear and goodabsorbance was acquired. Therefore, ethanol was chosen as the diluting agent. The effectof the volume of ethanol (30, 40, 50, 70, and 90 µL) on the extraction recovery wasalso studied. To investigate the influence of salt concentration on microextraction perfor-mance, various experiments were performed by adding different amounts of sodium nitrate(NaNO3; 0, 3, 6, 12, and 24%, w/v).

The tolerable limits of various foreign ions were studied in sample solution, spikedwith 20 µg L−1 of Cr(VI) by keeping the relative error at ±5%.

To validate the accuracy of the proposed procedure, recovery experiments were alsocarried out by spiking the samples with different amounts of Cr(VI) before any pre-treatment. Determination of Cr in the various samples by modified DLLME and atomicabsorption spectrometry detection was compared with other methods.

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Chromium(VI) in Saline Solutions 3403

Statistical Analysis

All the data were statistically analyzed using analysis of variance (ANOVA) to calculatethe difference in variables between dose treatments. The significance of the treatmenteffect was determined using the F-test, and to determine the significance of the differ-ence between the means of the two treatments, least significant differences (LSD) wereestimated at the 5% probability level.

Ionic Liquid–Based DLLME Procedure

To 10 mL of the sample or standard solution containing Cr, APDC 1.2 × 10−3 mol L−1

and acetate/acetic acid buffer (pH 5, 0.2 mol L−1) placed into a 15-mL screw-cap conical-bottom glass centrifuge tube, and 1 mL NaPF6 solution (200 mg L−1) was added. Then,500 µL of ethanol (as disperser solvent) containing 75 mg of [Hmim][PF6] (as extractionsolvent) was injected rapidly into the solution using a 1.0-mL syringe. A cloudy solutionthat consists of fine droplets of IL dispersed into solution was formed. The cloudy solutionwas shaken manually for several seconds and then centrifuged for 5 min at 5000 rpm. As aresult, the fine droplets of IL settled at the bottom of the centrifuge tube (approximately20 µL). Bulk aqueous phase was removed by a syringe. Afterward, IL phase was dissolvedin 50 µL ethanol and then 50 µL (for each analyte) was aspirated into the flame atomicabsorption spectrometer using a homemade microsample introduction system as describedin the previous work.

Results and Discussion

Optimization of the Procedure

As can be seen in Figure 1, by increasing the amount of [Hmim][PF6], the absorbanceincreased and then decreased due to increase in the volume of the settled phase. By increas-ing the volume of settled IL phase, viscosity of the IL–ethanol mixture increases. Whenthe viscosity of solution aspirated into the flame of the atomic absorption spectrometeris high, the nebulizer uptake rate and therefore the absorbance decreases. Thus, 70 mg[Hmim][PF6] was chosen for the subsequent experiments.

Figure 1. Effect of [Hmim][PF6] on the absorbance of the Cr. Conditions: Cr 50 µg L−1, APDC6.1 × 10−4 mol L−1 , buffer pH 5, NaPF6 200 mg mL−1, and ethanol 50 µL. Bars indicate meanvalue (n = 3) (color figure available online).

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3404 M. Taziki, F. Shemirani, and B. Majidi

To decrease the solubility of IL phase in brines, NaPF6 was added to the sample solu-tions as an ion-pairing agent. By adding NaPF6, [Hmim][PF6] was formed and accordingto common ion effect by increasing the amount of NaPF6, the solubility of [Hmim][PF6]decreased, so the absorbance increased. Thus, 1 mL NaPF6 was chosen for the subsequentexperiments (Figure 2).

The results illustrated in Figure 3 show that the absorbance rises with pH from 2 to5 and then declined with pH greater than 5.5. So, pH 5 was chosen as the optimum valuefor extraction. In all subsequent studies, the pH was adjusted to 5 by the addition of aceticacid–acetate buffer solution.

The result in Figure 4 showed that the absorbance of Cr increased by increasing theAPDC concentration up to 6.1 × 10−4 mol L−1 and then remained constant up to 1.2 ×10−3 mol L−1. A concentration of 6.1 × 10−4 mol L−1 of APDC was chosen for thesubsequent experiments.

The results obtained for volume of ethanol as the diluting agent are presented inFigure 5. As can be seen, 50 µL of ethanol was used in the subsequent experiments.

Figure 2. Effect of NaPF6 on the absorbance of the Cr. Conditions: Cr 50 µg L−1, APDC 6.1 × 10−4

mol L−1, buffer pH 5, [Hmim][PF6] 75 mg, and ethanol 50 µL. Bars indicate mean value (n = 3)(color figure available online).

Figure 3. Effect of pH on the absorbance of the Cr. Conditions: Cr 50 µg L−1, APDC 6.1 × 10−4

mol L−1, NaPF6 200 mg mL−1, [Hmim][PF6] 75 mg, and ethanol 50 µL. Bars indicate mean value(n = 3) (color figure available online).

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Chromium(VI) in Saline Solutions 3405

Figure 4. Effect of APDC on the absorbance of the Cr. Conditions: Cr 50 µg L−1, buffer pH 5,NaPF6 200 mg mL−1, [Hmim][PF6] 75 mg, and ethanol 50 µL. Bars indicate mean value (n = 3)(color figure available online).

Effect of Salt Concentration

In the presence of high medium salt content, the solubility of ILs increases and phaseseparation does not occur. However, according to the common ion effect, solubilitydecreases in the presence of common ion. NaNO3 was chosen to study the salt effect.Because of high solubility of NaNO3, salt effect was studied up to 40% (w/v). As shownin Figure 6 in the excess of NaPF6, phase separation occurred successfully. At greater saltcontent, the density of solution became greater than that of IL, which did not allow theextractant phase to settle.

Effects of Coexisting Ions

To demonstrate the selectivity of the developed microextraction system for the determina-tion of Cr(VI), the effect of other ions was evaluated. The tolerable concentration ratios offoreign ions to 20 µg L−1 Cr(VI) are shown in Table 1.

Figure 5. Effect of ethanol on the absorbance of the Cr. Conditions: Cr 50 µg L−1, APDC 6.1 ×10−4 mol L−1, buffer pH 5, NaPF6 200 mg mL−1, and [Hmim][PF6] 75 mg. Bars indicate mean value(n = 3) (color figure available online).

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3406 M. Taziki, F. Shemirani, and B. Majidi

Figure 6. Effect of amount NaNO3 on the absorbance of the Cr. Conditions: Cr 50 µg L−1, APDC6.1 × 10−4 mol L−1, buffer pH 5, NaPF6 200 mg mL−1, [Hmim][PF6] 75 mg, and ethanol 50 µL.Bars indicate mean value (n = 3) (color figure available online).

Evaluation of Method Performance

The analytical characteristics of the method were evaluated with the optimum experimentalconditions (Table 2). The calibration curve for Cr was linear up to 70 µg L−1 with acorrelation coefficient (r) of 0.9998. Limit of detection (LOD) based on three times thestandard deviation of the blank (3Sb) was 0.16 µg L−1 (n = 10), and the relative standarddeviation (RSD) for 20 µg L−1 of Cr was 2.68% (n = 10).

Analysis of Various Samples

The proposed methodology was applied for the determination of Cr(VI) in saline sam-ples including water samples (seawater, tap water) and food additives (sodium nitrate and

Table 1Effects of the foreign ions on the recovery of 20 µg L−1 of Cr(VI) from the

aqueous solutions

Ion Cr(VI) ratio (w/w) Recovery (%)

Li+ 10000 100.1Na+ 10000 99.8Pb(II) 200 97.4Cd(II) 100 98.3Al(X) 100 101.5Ca(II) 100 101.1Co(II) 100 98.2Zn(II) 100 97.6Mg(II) 100 103.2Cu(II) 100 98.6Ni(II) 50 103.5Mn(II) 50 98.7Fe(X) 50 99.1Cr(X) 50 96.4

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Chromium(VI) in Saline Solutions 3407

Table 2Analytical characteristics of modified DLLME method

Parameter Analytical feature

RSD (%) (n = 10)a 2.68%Linear range (µg L−1) 0.5−70Correlation coefficient (R2) 0.9998Limit of detection (µg L−1)b 0.16Enrichment factorc 162

aValues in parentheses are the Cr concentration (µgL−1) for which the RSD wasobtained.

bDetermined as 3Sb/m (where Sb and m are the standard deviation of the blank signaland the slope of the calibration graph, respectively).

cCalculated as the slope ratio of the calibration graph obtained with and withoutpreconcentration.

sodium acetate food grades). The important use of sodium acetate is in salt and vinegarchips. Sodium nitrate is used as a food preservative. Table 3 shows the obtained results.The results indicate that the proposed method can be reliably used for the determination ofCr in saline matrices.

Comparison to Other Methods

The results are shown in Table 4. The LOD of modified DLLME using only 10 mLof sample is better than that of other methods, and this method is robust against highmedium salt content (about 40%). The RSD of the proposed method is very low andpreconcentration factor is very high; all these results indicate that modified DLLME is

Table 3Determination of Cr(VI) in various samples by the proposed FAAS method and ETAAS

Sample Added Found)aRecovery

(%) ETAAS

Mineral waterb (units of µg L−1) 0 nd — nd10 9.41 ± 0.09 94.1 10.2

Seawaterc (units of µg L−1) 0 nd — 1.510 10.10 ± 0.12 101.1 11.7

River waterd (units of µg L−1) 0 3.84 ± 0.21 — 4.1510 13.34 ± 0.32 95 14.51

Sodium nitratee (units of ng g−1) 0 3.38 ± 0.17 — 3.810 13.60 ± 0.09 102.2 14

Sodium acetatee (units of ng g−1) 0 5.13 ± 0.13 — 5.310 15.20 ± 0.05 100.7 15.6

aMean of three experiments ± standard deviation.bFrom mineral water system of Damavand, Iran.cCaspian Sea water, Iran.dTehran River water.eFrom food grade.

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Chromium(VI) in Saline Solutions 3409

a reproducible, simple, and low-cost technique that can be used for the preconcentration ofmetal ions such as Cr from saline solution. The accuracy of the method was evaluated byanalysis in electrothermal atomic absorption spectrometry (ET-AAS).

Conclusions

In this study, proposed DLLME based on IL was successfully used for preconcentrationof Cr from saline samples. Determination was carried out by a flame atomic absorptionspectrometer. The developed procedure provided many merits such as low detection limit,excellent enrichment factor, and good RSD values. The results showed that the proposedIL-based DLLME is a powerful sample preparation technique for saline samples and canbe used instead of the traditional liquid–liquid extraction method. In addition, it openeda new perspective for the widening application of DLLME. The preconcentration methodwas successfully applied to the Cr(VI) determination in water samples and food-gradesalts, with good accuracy and reproducibility.

Acknowledgment

The authors extend their appreciation to University of Tehran for providing financialsupport to this research.

References

Beni, A., R. Karosi, and J. Posta. 2007. Speciation of hexavalent chromium in waters by liquid–liquidextraction and GFAAS determination. Microchemical Jounal 85:103–108.

Baghdadi, M., and F. Shemirani. 2009. In situ solvent formation microextraction based on ionicliquids: A novel sample preparation technique for determination of inorganic species in salinesolutions. Analytica Chimica Acta 634:186–191.

Chena, H., P. Dua, J. Chenb, S. Hub, S. Li, and H. Liua. 2010. Separation and preconcentration sys-tem based on ultrasonic probe–assisted ionic liquid dispersive liquid–liquid microextraction fordetermination trace amount of chromium(VI) by electrothermal atomic absorption spectrometry.Talanta 81:176–179.

Chen, W., G. P. Zhong, Z. D. Zhou, P. Wu, and X. D. Hou. 2005. Automation of liquid–liquidextraction–spectrophotometry using prolonged pseudo-liquid drops and handheld CCD forspeciation of Cr(VI) and Cr(III) in water samples. Analytical Science 21:1189–1193.

Chwastowska, J., W. Skwara, E. Sterlinska, and, L. Pszonicki. 2005. Speciation of chromium inmineral waters and salinas by solid-phase extraction and graphite furnace atomic absorptionspectrometry. Talanta 66:1345–1349.

Ezoddin, M., F. Shemirani, and R. Khani. 2010. Application of mixed-micelle cloud point extrac-tion for speciation analysis of chromium in water samples by electrothermal atomic absorptionspectrometry. Desalination 262:183–187.

Gharehbaghi, M., F. Shemirani, and M. D. Farahani. 2009. Cold-induced aggregation microextractionbased on ionic liquids and fiber optic–linear array detection spectrophotometry of cobalt inwater samples. Journal of Hazardous Materials 165:1049–1055.

Karatepe, A., E. Korkmaz, M. Soylak, and L. Elci. 2010. Development of a coprecipitation systemfor the speciation/preconcentration of chromium in tap waters. Journal of Hazardous Materials173:433–437.

Khani, R., F. Shemirani, and B. Majidi. 2011. Combination of dispersive liquid–liquidmicroextraction and flame atomic absorption spectrometry for preconcentration and determi-nation of copper in water samples. Desalination 266:238–243.

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3410 M. Taziki, F. Shemirani, and B. Majidi

Kiran, K., K. S. Kumar, B. Prasad, K. Suvardhan, L. R. Babu, and K. Janardhanam. 2008. Speciationdetermination of chromium(III) and (VI) using preconcentration cloud point extraction withflame atomic absorption spectrometry (FAAS). Journal of Hazardous Materials 150:582–586.

Kotas, J., and Z. Stasicka. 2000. Chromium occurrence in the environment and methods of itsspeciation. Environmental Pollution 107:263–283.

Krishna, P. G., J. M. Gladis, U. Rambabu, T. P. Rao, and G. R. K. Naidu. 2004. Preconcentrativeseparation of chromium(VI) species from chromium(III) by coprecipitation of its ethyl xanthatecomplex onto naphthalene. Talanta 63:541–546.

Kuban, P., and V. Kuban. 2003. Speciation of chromium(III) and chromium(VI) by capillaryelectrophoresis with contactless conductometric detection and dual opposite end injection.Electrophoresis 24:1397–1403.

Liang, P., and H. B. Sang. 2008. Speciation of chromium in water samples with cloud point extrac-tion separation and preconcentration and determination by graphite furnace atomic absorptionspectrometry. Journal of Hazardous Materials 154:1115–1119.

Maltez, H. F., and E. Carasek. 2005. Chromium speciation and preconcentration using zirconium(IV)and zirconium(IV) phosphate chemically immobilized onto silica gel surface using a flowsystem and F AAS. Talanta 65:537–542.

Meeravali, N. N., and S. J. Jiang. 2009. A novel cloud point extraction approach using cationicsurfactant for the separation and pre-concentration of chromium species in natural water priorto ICP-DRC-MS determination. Talanta 80:173–178.

Myers, C. R., J. M. Myers, B. P. Carstens, and W. E. Antholine. 2000. Reduction of chromium(VI)to chromium(V) by human microsomal enzymes: Effects of iron and quinines. Toxic SubstanceMechanisms 19:25–51.

Narayana, S. L., S. A. N. Reddy, Y. Subbarao, H. Inseong, and A. V. Reddy. 2010. Asimple and highly sensitive spectrophotometric determination of Cr(VI) in food samplesby using 3,4-dihydroxybenzaldehydeisonicotinoylhydrazone (3,4-DHBINH). Food Chemistry121:1269–1273.

Narin, I., A. Kars, and M. Soylak. 2008. A novel solid phase extraction procedure on AmberliteXAD-1180 for speciation of Cr(III), Cr(VI), and total chromium in environmental andpharmaceutical samples. Journal of Hazardous Materials 150:453–458.

Paleologos, E. K., C. D. Stalikas, and M. I. Karayannis. 2001. An optimised single-reagent methodfor the speciation of chromium by flame atomic absorption spectrometry based on surfactantmicelle-mediated methodology. Analyst 126:389–393.

Paleologos, E. K., C. D. Stalikas, S. M. T. Karayanni, G. A. Pilidis, and M. I. Karayannis.2000. Micelle-mediated methodology for speciation of chromium by flame atomic absorptionspectrometry. Journal of Analytical Atomic Spectrometry 15:287–291.

Paquet, P. M., J. F. Gravel, P. Nobert, and D. Boudreau. 1998. Speciation of chromium byion chromatography and laser-enhanced ionization: Optimization of the excitation–ionizationscheme. Spectrochimica Acta Part B 53:1907–1917.

Pramanik, S., S. Dey, and P. Chattopadhyay. 2007. A new chelating resin containing azophenolcar-boxylate functionality: Synthesis, characterization, and application to chromium speciation inwastewater. Analytica Chimica Acta 584:469–476.

Tang, A. N., D. Q. Jiang, Y. Jiang, S. W. Wang, and X. P. Yan. 2004. Cloud point extraction forhigh-performance liquid chromatographic speciation of Cr(III) and Cr(VI) in aqueous solutions.Journal of Chromatography B 1036:183–188.

Tunceli, A., and A. R. Turker. 2002. Speciation of Cr(III) and Cr(VI) in water after preconcentrationof its 1,5-diphenylcarbazone complex on amberlite XAD-16 resin and determination by FAAS.Talanta 57:1199–1204.

Tuzen, M., and M. Soylak. 2007. Multiwalled carbon nanotubes for speciation of chromium inenvironmental samples. Journal of Hazardous Materials 147:219–225.

Wang, L., B. Hu, Z. C. Jiang, and Z. Q. Li. 2002. Speciation of Cr-III and Cr-VI in aqueous sam-ples by coprecipitation/slurry sampling fluorination-assisted graphite furnace atomic absorptionspectrometry. International Journal of Environmental Analytical Chemistry 82:387–393.

Dow

nloa

ded

by [

Flor

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Stat

e U

nive

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Chromium(VI) in Saline Solutions 3411

Wang, Z. H., M. Song, Q. L. Ma, H. M. Ma, and S. C. Liang. 2000. Two-phase aqueous extractionof chromium and its application to speciation analysis of chromium in plasma. MicrochemicalJournal 134:95–99.

Yamini, Y., M. Rezaee, A. Khanchi, M. Faraji, and A. Saleh. 2010. Dispersive liquid–liquidmicroextraction based on the solidification of floating organic drop followed by induc-tively coupled plasma–optical emission spectrometry as a fast technique for the simultaneousdetermination of heavy metals. Journal of Chromatography A 1217:2358–2364.

Yeh, C. F., and S. J. Jiang. 2004. Speciation of V, Cr, and Fe by capillary electrophoresis–bandpassreaction cell inductively coupled plasma mass spectrometry. Journal of Chromatography A1029:255–261.

Yousefi, S. R., and F. Shemirani. 2010. Development of a robust ionic liquid–based dispersive liquid–liquid microextraction against high concentration of salt for preconcentration of trace metals insaline aqueous samples: Application to the determination of Pb and Cd. Analytica Chimica Acta669:25–31.

Zang, X. H., Q. H. Wu, M. Y. Zhang, G. H. Xi, and Z. Wang. 2009. Developments of dispersiveliquid–liquid microextraction technique. Chinese Journal of Analytical Chemistry 37:161–168.

Zhitkovich, A., G. Quievryn, J. Messer, and Z. Motylevich. 2002. Reductive activation with cysteinerepresents a chromium(III)-dependent pathway in the induction of genotoxicity by carcinogenicchromium(VI). Environmental Health Perspectives 110:729–731.

Zhu, X. S., B. Hu, Z. C. Jiang, and M. F. Li. 2005. Cloud point extraction for speciation ofchromium in water samples by electrothermal atomic absorption spectrometry. Water Research39:589–595.

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