Switchable polarity solvent for liquid phase microextraction of Cd(II) as pyrrolidinedithiocarbamate chelates from environmental samples

Analytica Chimica Acta 886 (2015) 75e82

Contents lists available at ScienceDirect

Analytica Chimica Acta journal homepage: www.elsevier.com/locate/aca

Switchable polarity solvent for liquid phase microextraction of Cd(II) as pyrrolidinedithiocarbamate chelates from environmental samples* Erkan Yilmaz, Mustafa Soylak* Erciyes University, Faculty of Sciences, Department of Chemistry, 38039 Kayseri, Turkey

h i g h l i g h t s

g r a p h i c a l a b s t r a c t


Switchable polarity solvent was synthesized from triethylamine (TEA)/ water/CO2.
The switchable polarity solvent has been used for the microextraction of cadmium(II).
The important factors were optimized.
The method was applied to determination of cadmium in real samples.

a r t i c l e i n f o

a b s t r a c t

Article history: Received 5 January 2015 Received in revised form 3 May 2015 Accepted 2 June 2015 Available online 9 July 2015

A switchable polarity solvent was synthesized from triethylamine (TEA)/water/CO2 (Dry ice) via proton transfer reaction has been used for the microextraction of cadmium(II) as pyrrolidinedithiocarbamate (APDC) chelate. Cd(II)-APDC chelate was extracted into the switchable polarity solvent drops by adding 2 mL 10 M sodium hydroxide solution. Analytical parameters affecting the complex formation and microextraction efficiency such as pH, amount of ligand, volume of switchable polarity solvent and NaOH, sample volume were optimized. The effects of foreign ions were found tolerably. Under optimum conditions, the detection limit was 0.16 mg L1 (3Sb/m, n ¼ 7) and the relative standard deviation was 5.4% (n ¼ 7). The method was validated by the analysis of certified reference materials (TMDA-51.3 fortified water, TMDA-53.3 fortified water and SPS-WW2 waste water, 1573a Tomato Leaves and Oriental Basma Tobacco Leaves (INCT-OBTL-5)) and addition/recovery tests. The method was successfully applied to determination of cadmium contents of water, vegetable, fruit and cigarette samples. © 2015 Elsevier B.V. All rights reserved.

Keywords: Switchable polarity solvent Green chemistry Cadmium Preconcentration Proton transfer reaction Liquid phase microextraction

1. Introduction Toxic metal pollution of the environment has received considerable attention. Cadmium is known to be a highly toxic element. Cadmium could be harmful to plants, animals and accumulates in humans, particularly in the kidneys over relatively long durations of 20e30 years [1e3]. The international agency for research on

*

This study is a part of PhD thesis of Erkan Yilmaz. * Corresponding author. E-mail addresses: [email protected] (E. Yilmaz), soylak@erciyes. edu.tr (M. Soylak). http://dx.doi.org/10.1016/j.aca.2015.06.021 0003-2670/© 2015 Elsevier B.V. All rights reserved.

cancer has categorized cadmium as a human carcinogen and several reports have shown some dramatic increase of cadmiumdependent diseases [4,5]. The limit for cadmium in water samples was given as lover than 5 mg/L [6], while it was given for food samples in the range of 0.05e5 mg/kg [7]. The effective and simple analytical methods for determining and evaluating trace levels of cadmium in various types of matrices such as water, food, biological and environmental samples has a important place for protecting the health of humans [8e10]. Trace levels of cadmium in real samples are fairly lower than detection limits of instrumental analysis available in laboratories (flame atomic absorption spectroscopy (FAAS), inductively coupled

76

E. Yilmaz, M. Soylak / Analytica Chimica Acta 886 (2015) 75e82

plasma-optical emission spectrometry (ICP-OES) and graphite furnace-atomic absorption spectrometry (GF-AAS)) and the interference due to matrix in real samples cannot be always eliminated [11e15]. Separation and preconcentration methods are necessary to eliminate or minimize matrix effects and achieve high extraction efficiencies [16]. Several separation-preconcentration techniques such as solid phase extraction (SPE) [17], co-precipitation [18], cloud point extraction (CPE) [19] and liquideliquid extraction (LLE) [20] have been developed for the separation and preconcentration of metals from environmental samples. In these techniques, large amounts of potentially toxic organic solvents which are often hazardous due to their high vapor pressure and produce secondary wastes along procedure were used [21e25]. To overcome these limitations of the conventional analytical techniques, up to now, a range of homogeneous liquideliquid microextraction method, which can be considered under the Green Chemistry have been developed [25e28]. The development of novel solvents for microextraction studies provides an opportunity to extend the concepts and practices of green chemistry [29,30]. A new generation solvents called switchable-polarity solvents (SPs) has received attention as solvent alternatives due to their reversibly change physical properties abruptly [31,32]. The switchable solvents defined as a system in which a non-ionic liquid converts to an ionic liquid under the presence of carbon dioxide and then reverts back to its non-ionic form when the gas is purged from the solution [31e35]. The possibility of using carbon dioxide to reversibly switch the polarity of a medium provides a promising tool for the design of eco-efficient methods. At the same time, the low cost and non-toxic nature of CO2 makes it an ideal phase transition trigger in extraction techniques. The main advantages of using of SPs are that allows the extraction of the analytes in a homogeneous phase without dispersive solvent and easy phase separation without additional apparatus. SPs are environmentally friendly compounds [31e38]. This work is the first report on the switchable-polarity solvent based liquid phase microextraction technique for the separation and preconcentration of heavy metal ions. In this work, the suitability of switchable-polarity solvent based liquid phase microextraction technique (SPs- LLME) for the separation and preconcentration of cadmium in real samples prior to its micro sampling flame atomic absorption spectrometric determinations was explored. 2. Experimental 2.1. Reagents and standards All chemicals used in experiment were analytical reagent grade and were used without further purification. The used water was deionised (18.2 MU cm, Millipore). CO2 (Dry ice) was provided by Ates Company (Kahramanmaras, Turkey). Triethylamine, NaOH, Concentrated 30% (v/v) H2O2 and 65% HNO3 were purchased from E. Merck Company (Darmstadt, Germany). A stock solution of a concentration of 1000 mg L1 of cadmium(II) was prepared by dissolving appropriate amounts of cadmium (II) nitrate at in 0.01 mol L1 HNO3 (Merck, Darmstadt, Germany) and solutions for calibration were prepared before use by further dilutions with 0.01 mol L1 HNO3. External calibration standards were not subjected to the separation-preconcentration procedure. A 0.1% (w/v) ammonium pyrrolidinedithiocarbamate (APDC) obtained from SigmaeAldrich (St. Loius, MO, USA) was prepared with using ethanol. The pH values were adjusted by addition of phosphate buffer 1 solutions (0.1 mol L1 H2PO H3PO4) for pH 2e3, ace4 /0.1 mol L tate buffer solutions (0.1 mol L1 CH3COO/0.1 mol L1 CH3COOH)

for pH 4e5, phosphate buffer solutions (0.1 mol L1 NaH2PO4 / 0.1 mol L1 Na2HPO4) for pH 6e7 and ammonium buffer solutions 1 (0.1 mol L1 NHþ NH3) for 8. 4 /0.1 mol L 2.2. Instrumentation An Analyst 300 Model flame atomic absorption spectrometer (Norwalk, CT, USA) including a cadmium hollow cathode lamp (operated conditions as follows: wavelength 228.8 nm, spectral band width: 0.7 nm and lamp current: 6.0 mA) and aireacetylene flame was used for absorbance measurements. The samples were injected to the FAAS by using micro injection system, which consist of a mini home-made Teflon funnel with an Eppendorf Pipette. The Teflon funnel was connected to the nebulizer of FAAS with capillary tubing. The measurements were performed with the continuous aspiration mode of FAAS. A 100 mL of extraction phase was injected to the micro-injection unit by using Eppendorf pipette and peak heights were recorded as signals [16,29]. A centrifuge with centrifugal vials ((ALC PK 120 Model, Buckinghamshire, England) was used for phase separation. The FT-IR spectra of the switchable solvents (triethylamine (TEA) and protonated triethylamine carbonate (P-TEA-C)) were recorded by using the PerkineElmer Spectrum 400 FT-IR spectrometer (Waltham, MA, USA). The 1H NMR spectra were recorded at 297 K on a Bruker 400 nuclear magnetic resonance spectrometer at 400 MHz. 2.3. Synthesis of switchable solvent 200 mL of Milli-Q water and 200 mL of triethylamine were added in a 1 L glass bottle on magnetic stirrer and a two phase system formed. Then, Dry ice (20 g) was added gradually on the two phase system under vigorous stirring. After completely dissolution of CO2, amine phase became cloudy. The addition of dry ice was repeated twenty times until obtain a single phase obtained, which corresponds to a 1:1 (v:v) water/Triethylamine solution, was obtained. Afterward, the mixture was stirred for 2 h at room temperature to ensure the complete protonation of triethylamine. The synthesis reaction and mechanism was given and reviewed in literature [39e41]. The high volume of the bottle employed in this synthesis allows the use of this amount of dry ice without a risky increase of the internal pressure. 400 mL of the switchable solvent can be easily prepared and this volume allows the using of more than 450 extractions. Since only 750 mL of the switchable solvent was used for each experiment for microextraction procedure. 2.4. Switchable solvent based microextraction procedure A schematic diagram of the preconcentration and determination system is shown in Fig. 1. Ten mL of model solution containing Cd(II), 1.25 mL of 0.1% (w/v) APDC solution and 2 mL of related buffer solution were transferred to a 50 mL centrifuge tube. First, 750 mL of aqueous amine (Protonated triethylamine carbonate) was added to in the centrifuge tube and the centrifuge tube was shaken manually for 5 s until a homogeneous phase was observed. Then, 2.0 mL of 10 M NaOH solution was added and a cloudy solution appeared in the centrifuge tube. At this stage, Cd-APDC complex in the aqueous phase were extracted into the fine droplets of triethylamine phase. The cloudy solution was centrifuged at 4000 rpm for 6 min to accelerate the complete separation of the water and triethylamine phase. The triethylamine phase was collected on the surface of the water phase. The triethylamine phase (approximately 100e150 mL) was taken with micropipette and its volume completed to 500 mL with concentrated HNO3. Finally, 100 mL of the

E. Yilmaz, M. Soylak / Analytica Chimica Acta 886 (2015) 75e82

77

Fig. 1. Graphical representation of the switchable-polarity solvent based liquideliquid microextraction technique (SPs- LLME).

extraction phase was aspirated into the flame AAS nebulizer using a microinjection system in continuous aspiration mode. 2.5. Applications The developed microextraction method was applied to TMDA51.3 fortified water, TMDA-53.3 fortified water and SPS-WW2 waste water certified reference materials and water samples from Kayseri/Turkey. The water samples collected in polyethylene bottles and filtered through a cellulose membrane filter (Millipore) of 0.45 mm pore size prior to use. The procedure given in Section 2.4 was applied to 10 mL of each water samples. Certified reference materials (1573a Tomato Leaves and Oriental Basma Tobacco Leaves (INCT-OBTL-5)), vegetable, fruit and cigarette samples were used for the application of the presented method. The vegetable, fruit and cigarette samples were dried at temperature 80  C for 24 h and homogenized using an agate mortar and pestle. A wet ashing procedure was used for digestion of the samples. 0.10 g of certified reference materials and/or 0.25 g of vegetable,

fruit and cigarette samples were weighed into beakers and digested with 10 mL concentrated HNO3 at 95  C on hot plate. After cooling, the residue was again digested with mixtures of hydrogen peroxide (5 mL) and concentrated HNO3 (15 mL) until dryness. The residues in beakers were dissolved with 5 mL distilled water and filtered. The analysis was followed as indicated in the Section 2.4. 3. Results and discussion 3.1. Characterization of switchable solvent When the water-immiscible solvent (triethylamine) can be solubilized in 1:1 ratio using an atmosphere of carbon dioxide as reagent reacted with sodium hydroxide solution, two phases were obtained via a change on the ionization state of the amine. Changes in the ionization state of the amine and physical properties resulting from the change from low polarity to high polarity and again low polarity were confirmed by ATR-FT-IR and 1H NMR spectroscopy.

Fig. 2. FT-IR spectra of the TEA and P-TEA-C.

78

E. Yilmaz, M. Soylak / Analytica Chimica Acta 886 (2015) 75e82

Fig. 3. (a). 1H NMR spectra of TEA (b). 1H NMR spectra of TEA P-TEA-C.

The FT-IR spectra of TEA and P-TEA-C (A and B) are shown in Fig. 2. The FT-IR spectrum of TEA shows typical bands at 2967.63 cm1, 2937.53 cm1 and 2873.57 cm1, 1388.13 cm1, and 1345.16 cm1 for CH2-asymetric stretching vibration, eCH2symetric stretching vibration, CeN stretching vibrations, respectively. When P-TEA-C was synthesized, several new peaks appeared in the spectrum, the most significant changes have been observed in at 3252.21 cm1 and 1611.87 cm1 for NeH stretching and NeH bending vibrations, respectively and these peaks are characteristic for NeH stretches of amines. The other peaks at 1175.18 cm1, 1062.91 cm1 and 1012.26 cm1 for CeN stretching vibrations. The 1H NMR spectra of TEA and P-TEA-C (A and B) are shown in Fig. 3. The typical H NMR bands of TEA (A) (CDCl3, ppm) shows at 0.97 (t, 9H, J ¼ 8 Hz, eCH3), 2.47(q, 6H, J ¼ 8 Hz, eCH2), respectively. For 1H NMR of P-TEA-C, several new bands appeared at 1.05 (t, 3H, J ¼ 8 Hz, eCH3), 1.23 (t, 6H, J ¼ 8 Hz, eCH3), 1.29 (br., 2H, eOH), 1.94 (s, 1H, eNH), 2.53 (q, 2H, J ¼ 8 Hz, eCH2), 3.13 (q, 4H, J ¼ 8 Hz, eCH2) and 3.18 (br., 2H, eOH), respectively (Fig 3).

3.2. Optimization All optimization works were performed by using model solutions that contain analyte ions. The recovery, %, value for cadmium(II) was calculated using the following relationship:


.  Recovery; % ¼ wo wf  100; where wo (mg) is amount of cadmium(II) in final solution and wf (mg) is amount of cadmium(II) in beginning solution, respectively. 3.2.1. Effect of pH The pH value of the donor phase has a key role for hydrophobic metal complex formation and extraction efficiency. The effect of the pH on complex formation and the extraction of Cd(II) was studied in the range of 2.0e8.0. The results are depicted in Fig. 4. The quantitative recoveries were obtained between pH 2.0e6.0. These results were agree with the extraction works about metal ions with

E. Yilmaz, M. Soylak / Analytica Chimica Acta 886 (2015) 75e82

Fig. 4. Effect of pH on the recovery of Cd(II) (APDC: 1.25 mg, volume of the Extractant solution: 1.0 mL, volume of the 10 M NaOH solution: 2.0 mL, N ¼ 3).

APDC. The recoveries of metal ions by using with APDC are generally quantitative at acidic pHs [42,43] and are not quantitative at basic pHs [42,43]. All of the subsequent experiments were performed at pH 4.0. 3.2.2. Effect of APDC amount APDC forms very stable and hydrophobic complexes rapidly with metal species, which provide solubility of metal complex in extraction phase [16]. The effect of volume of 0.1% (w/v) APDC solution on the recovery of Cd(II) was investigated in the range of 0.0e1.5 mL by using the developed microextraction method. The results are given in Fig. 5. The recovery of cadmium(II) without APDC was 25%. The recovery of Cd(II) was increased with increasing volume of APDC and reach quantitative value at 1.0 mL of 0.1% (w/v) APDC solution. It was quantitative in the range of 1.0e1.5 mL of 0.1% (w/v) APDC solution. 1.25 mL of APDC was selected as optimum value.

79

Fig. 6. Effect of the Extractant volume on the recovery of Cd(II) (pH: 4.0, APDC: 1.25 mg, volume of 10 M NaOH solution: 2.0 mL, N ¼ 3).

the extraction efficiency was studied in the volume range of 0.25 mLe1.25 mL by using 2 mL of 10 M NaOH. As can be seen in Fig. 6, the quantitative recoveries were achieved over the volume of protonated triethylamine carbonate range of 0.5e1.25 mL. Hence, based on the obtained experimental data, 0.75 mL of protonated triethylamine carbonate was used in all subsequent experiments.

3.2.3. Effect of protonated triethylamine carbonate volume Triethylamine (immiscible water form of switchable polarity solvents) and protonated triethylamine (miscible form of switchable polarity solvents) can be switched between the two forms by the addition or removal of CO2 from the system. Triethylamine/ protonated triethylamine carbonate pair was used for the extraction of hydrophobic Cd(II)-APDC complex from sample solution. The effect of the volume of protonated triethylamine carbonate on

3.2.4. Effect of NaOH NaOH is necessary for the induce phases separation and separation of the phases in the presented microextraction system [44]. To extract and isolate the Cd(II)-APDC complex from water phase including protonated triethylamine carbonate, the hydrophilic bicarbonate salt of the protonated triethylamine was converted to hydrophobic triethylamine form by using 10 M of NaOH. For this purpose, a series of sample solution containing 1.25 mg APDC were studied by using 0.75 mL of P-TEA-C and different volumes of 10 M NaOH solution in range of 1.0e3.5 mL to find optimum NaOH volume. The results are given in Fig. 7 reveal that the quantitative recoveries were obtained 1.75 and 2.0 mL of 10 M NaOH. Further increase in volume of NaOH caused decrease in extraction efficiency because the hydrophobic triethylamine phase was not occurred and therefore the phase separation is possible in the range of 1.75 and 2.0 mL of 10 M NaOH. By the addition of NaOH, the phase separation is immediately started and completed in five seconds. In this period, the Cd-APDC complex was quantitatively

Fig. 5. Effect of the APDC amount on the recovery of Cd(II) (pH: 4.0, volume of the Extractant solution: 1.0 mL, volume of the 10 M NaOH solution: 2.0 mL, N ¼ 3).

Fig. 7. Effect of the 10 M NaOH volume on the recovery of Cd(II) (pH: 4.0, APDC: 1.25 mg, volume of extractant solution: 0.75 mL, N ¼ 3).

80

E. Yilmaz, M. Soylak / Analytica Chimica Acta 886 (2015) 75e82

Table 1 Effects of some matrix ions on the recovery of Cd(II) (pH: 4.0, APDC: 1.25 mg, volume of the Extractant solution: 0.75 mL, volume of the 10 M NaOH solution: 2.0 mL, N ¼ 3). Ion þ

Na Kþ Mg2þ Ca2þ Fe3þ Mn2þ Zn2þ Ni2þ Co2þ Cl SO2 4 F-

Added as

Concentration mg L1 Matrix ion/Cd2þ Recovery, %

NaNO3 KCl Mg(NO3)2.6H2O Ca(NO3)2.4H2O Fe(NO3)3 9H2O Mn(NO3)2.4H2O Zn(NO3)2.6H2O Ni(NO3)2.6H2O Co(NO3)2.6H2O KCl Na2SO4 NaF

5000 1000 500 500 2.5 5 10 5 10 1000 1000 1000

75000 15000 7500 7500 150 75 150 75 150 15000 15000 15000

101 95 99 99 99 100 101 97 99 95 93 96

± ± ± ± ± ± ± ± ± ± ± ±

Table 4 The application of the developed SPs-LLME method for determination of cadmium in vegetable, fruit and cigarette samples (pH: 4.0, APDC: 1.25 mg, Volume of the Extractant solution: 0.75 mL, Volume of the 10 M NaOH solution: 2.0 mL, N ¼ 3).

4 4 7 1 1 7 2 4 1 4 0 0

extracted to switchable solvent phase. The pH of aqueous phase was 12.0 and the pH of switchable solvent phase is pH 8.0. Two mL of 10 M NaOH was selected as optimum volume. 3.2.5. Effect of sample volume In this work, the effect of sample volume were studied with applying different volumes of solutions with same concentrations of cadmium(II). The developed microextraction method was applied to different volumes of analyte solution (5e30 mL) keeping other conditions constant to investigate effect of sample volume on the recoveries of analyze ion. The results show that the extraction of cadmium(II) was not affected by a sample volume below 15 mL. 3.2.6. Effect of matrix The influences of the matrix components of environmental samples are an important problem in the flame atomic absorption spectrometric determination of trace metal in these samples

Sample

Concentration, mg g1

Lettuce Zucchini Eggplant Thyme Cigarette-III Cigarette-IV Cigarette-V Cigarette-VI

0.15 ± BDLa BDL BDL 0.63 ± 1.24 ± 1.38 ± 1.18 ±

a b

0.02

0.07b 0.09 0.03 0.023

BDL: Below the detection limit. Mean ± standard deviation.

[45e49]. The effect of common coexisting ions on SPs-LLME of Cd(II) was investigated. The effects of investigated matrix ions were tested separately. The obtained recovery results for the studied matrix ions are given in Table 1. The results showed that the possible matrix ions in various real samples have no obvious effect on the selective microextraction and determination of Cd(II) under the selected conditions.

3.3. Figures of merits Limit of detection (LOD), relative standard deviation (RSD), calibration curve and enhancement factor (EF) were investigated under the optimized experimental conditions. The LOD, was found as the ratio of three times standard deviation of seven blank absorbencies to the slope of the regression equation, was 0.16 mg L1. The limit of qualification was calculated as the ratio of ten times the standard deviation of seven blank solutions to the slope of the

Table 2 The analysis results of 0.53e167 microgram certified reference materials (pH: 4.0, APDC: 1.25 mg, Volume of the Extractant solution: 0.75 mL, Volume of the 10 M NaOH solution: 2.0 mL, N ¼ 3). pffiffiffiffi Certified reference material Certified value, mg L1 Found, mg L1 (x-m) ±ts= N TMDA-51.3 Lake Ontario Water TMDA-53.3 SPS-WW2 Waste Water

24.15 ± 0.78 118 ± 4 97 ± 6 Found, mg g1 1.41 ± 0.003 2.62 ± 0.04

25.9 118 100 ± 0.5 Certified value, mg g1 1.52 ± 0.04 2.64 ± 0.14

1573a Tomato Leaves Oriental BasmaTobacco Leaves (INCT-OBTL-5)

1.75 0 3

1.94 9.94 14.9

0.11 0.02

0.0075 0.0993

t: 4.303, % 95 confidence interval. x: mean value. m: SRM value.

Table 3 Addition and recovery test for SPs-LLME of cadmium in water, vegetable, fruit and cigarette samples (pH: 4.0, APDC: 1.25 mg, Volume of the Extractant solution: 0.75 mL, Volume of the 10 M NaOH solution: 2.0 mL, N ¼ 3). Samples

Added mg

Found mg

Recovery%

Samples

Added mg

Found mg

Dam water

0.00 0.15 0.30 0.0 0.15 0.30 0.00 0.25 0.50 0.00 0.20 0.40

BDLa 0.151 0.306 0.030 0.179 0.346 BDL 0.251 0.501 0.043 0.254 0.439

e 101 102 e 99 105 e 100 100 e 104 102

Dem water

0.00 0.25 0.50 0.00 0.20 0.40 0.00 0.25 0.50 0.00 0.25 0.50

BDL 0.254 0.516 BDL 0.197 0.387 0.036 0.280 0.502 0.074 0.333 0.589

Tomato

Green pepper

Cigarette-I

a b

BDL: Below the detection limit. Mean ± standard deviation.

± ± ± ± ±

0.002b 0.006 0.002 0.009 0.004

± ± ± ± ±

0.010 0.006 0.002 0.009 0.009

Peach

Parsley

Cigarette-II

± 0.006 ± 0.006 ± ± ± ± ± ± ± ±

0.000 0.015 0.003 0.017 0.009 0.006 0.007 0.016

Recovery% 102 103 99 97 98 94 102 103

E. Yilmaz, M. Soylak / Analytica Chimica Acta 886 (2015) 75e82

81

Table 5 Comparison of the SPs-LLME with other methods for the determination of cadmium in real samples with FAAS. Method

LOD, mg L1

Enhancement factor

Samples

Ref.

Solid phase extraction In situ solvent formation microextraction Hollow fiber renewal liquid membrane Ultrasound-assisted emulsificationemicroextraction Cloud point extraction Coprecipitation Solid phase extraction Switchable-polarity solvent based liquideliquid microextraction

2.8 0.07 1.3 0.91 0.099 0.27 0.45 0.16

15 78 120 13.4 57.7 25 80 30

Food Water, Water Water Water Water, Water, Water,

[17] [50] [51] [52] [53] [54] [55] This work

regression equation was 0.53 mg L1. The average relative standard deviation (RSD) was 5.4% for five repeated determinations of 20 mg L1. The calibration curve, which based on the relationship between the absorbance (A) of cadmium in the FAAS measurement and the concentration of cadmium as mg/L (C) was A ¼ 1.4  104 þ 0.226C with a correlation coefficient (R2 ¼ 0.999). The linear range for calibration curve of cadmium was in the range of 0.53e157 microgram/L. The enhancement factor (EF), which calculated by using the ratio of the cadmium concentration in the switchable extraction phase to the initial concentration of cadmium in the sample solution, was found as 28.1. 3.4. Applications of the method The applicability of the developed microextraction procedure was assessed by preconcentration and determination of the cadmium in TMDA-51.3 fortified water, TMDA-53.3 fortified water, SPS-WW2 waste water, 1573a Tomato Leaves and Oriental Basma Tobacco Leaves (INCT-OBTL-5) certified reference materials. The obtained results (Table 2) indicate that the recoveries in the range of 93e100 % are reasonably well for trace amount of cadmium in real samples. The addition-recovery experiments for water, vegetable, fruit and cigarette samples were performed to evaluate the accuracy and applicability of the developed switchable polarity solvents microextraction method. The results given Table 3 demonstrated that the samples matrices, in our present context, had no effect on SPsLLME of cadmium. The method was successfully applied to microextraction and determination of cadmium in vegetable, fruit and cigarette samples collected from markets in Kayseri/Turkey (Table 4). Comparison with the previously was reported preconcentration methods shown in Table 5. A similar or superior performance with respect to limit of detection, enhancement factor and relative standard deviation was achieved. 4. Conclusion When compared with other microextraction methods, the properties of switchable solvents for microextraction studies provides some advantages; (I) No use huge amount organic dispersive solvent for dispersion of extraction phase to water phase and because of this advantage no produce secondary waste (II) The protonated triethylamine bicarbonate solution was stable at least for 10 months and used for 450 experiments. (III) No need specific laboratory equipments like vortex and ultrasonic radiation source, which are used in microextraction methods to obtain homogeneous mixture. (IV) No need complex processes like cooling, heating, air assistance, pressure assistance and addition of salt for formation of extraction phase. The other advantages of the method are that can be applied to water, vegetable, fruit and cigarette

food grade salts

food soil, ore vegetable, fruit, cigarette

samples without matrix interferences with low detection limit (0.16 mg L1) and good repeatability (5.4%). Acknowledgment The authors are grateful for the financial support of the Unit of the Scientific Research Projects of Erciyes University (FBA-20155783) (Kayseri, Turkey). References [1] H.G. Seiler, A. Sigel, H. Sigel, Handbook on Toxicity of Inorganic Compounds, Marcel Dekker, New York, 1998. [2] M. Tuzen, M. Soylak, Determination of trace metals in canned fish marketed in Turkey, Food Chem. 101 (2007) 1378. [3] A.C. Davis, P. Wu, X.F. Zhang, X.D. Hou, B.T. Jones, Determination of cadmium in biological samples, Appl. Spectrosc. Rev. 41 (2006) 35. [4] A. Chahid, M. Hilali, A. Benlhachimi, T. Bouzid, Contents of cadmium, mercury and lead in fish from the Atlantic sea (Morocco) determined by atomic absorption spectrometry, Food Chem. 147 (2014) 357. [5] A. Vural, I. Narin, M.E. Erkan, M. Soylak, Trace Metal Levels, Some Chemical, Parameters in herby cheese collected from South Eastern Anatolia-Turkey, Environ. Monit. Assess. 139 (2008) 27. [6] S. Khan, M. Soylak, T.G. Kazi, Room temperature ionic liquid-based dispersive liquid phase microextraction for the separation/preconcentration of trace Cd2þ with 1-(2-pyridylazo)-2-naphthol (PAN) complex from environmental and biological samples using and determined by FAAS, Biol. Trace Elem. Res. 156 (2013) 49. [7] http://www.atsdr.cdc.gov/csem/csem.asp?csem¼6&po¼7, (assessed on April 2015). [8] I. Rutyna, M. Korolczuk, Determination of lead and cadmium by anodic stripping voltammetry at bismuth film electrodes following double deposition and stripping steps, sensor, Actuator B-Chem. 204 (2014) 136. [9] X.Y. Hu, K. Zhu, Q.S. Guo, Y.Q. Liu, M.F. Ye, Q.J. Sun, Ligand displacementinduced fluorescence switch of quantum dots for ultrasensitive detection of cadmium ions, Anal. Chim. Acta 812 (2014) 191. [10] S. Khan, E. Yilmaz, T.G. Kazi, M. Soylak, Vortex assisted liquideliquid microextraction using Triton X-114 for ultratrace cadmium prior to analysis, Clean 42 (2014) 1083. [11] S.L.C. Ferreira, J.B. de Andrade, M.G.A. Korn, M.G. Pereira, V.A. Lemos, W.N.L. dos Santos, F.M. Rodrigues, A.S. Souza, H.S. Ferreira, E.G.P. da Silva, Review of procedures involving separation and preconcentration for the determination of cadmium using spectrometric techniques, J. Hazard. Mater. 145 (2007) 358. [12] M. Khairy, S.A. El-Safty, M.A. Shenashen, Environmental remediation and monitoring of cadmium, TRAC- Trend Anal. Chem. 62 (2014) 56. [13] K. Pyrzynska, K. Kilian, On-line sorption-based systems for determination of cadmium with atomic spectrometry detectors, Water Res. 41 (2007) 2839. [14] K. Pyrzynska, Online sample pretreatment systems for determination of cadmium by the ETAAS method, Crit. Rev. Anal. Chem. 37 (2007) 39. [15] H. Chen, J. Han, Y. Wang, Y.T. Hu, L. Ni, Y.Y. Liu, W.B. Kang, Y. Liu, Hollow fiber liquid-phase microextraction of cadmium(II) using an ionic liquid as the extractant, Microchim. Acta 181 (2014) 1455. [16] M. Soylak, E. Yilmaz, Determination of cadmium in fruit and vegetables by ionic liquid magnetic microextraction and flame atomic absorption spectrometry, Anal. Lett. 48 (2015) 464. [17] Z.A. ALOthman, M. Habila, E. Yilmaz, M. Soylak, Solid phase extraction of Cd(II), Pb(II), Zn(II) and Ni(II)from food samples using multiwalled carbon nanotubes impregnated with 4-(2-thiazolylazo)resorcinol, Microchim. Acta 177 (2012) 397. [18] F. Tokay, S. Bagdat, Determination of iron and copper in edible oils by flame atomic absorption spectrometry after liquid-liquid extraction, J. Am. Oil Chem. Soc. 92 (2015) 317. [19] M. Soylak, E. Yilmaz, M. Ghaedi, M. Montazerozohori, M. Sheibani, Cloud point extraction and flame atomic absorption spectrometry determination of Lead(II) in environmental and food samples, J. AOAC Int. 95 (2012) 1797.

82

E. Yilmaz, M. Soylak / Analytica Chimica Acta 886 (2015) 75e82

[20] A.N. Anthemidis, G.A. Zachariadis, G.F. Charalampos, J.A. Stratis, On-line liquideliquid extraction system using a new phase separator for flame atomic absorption spectrometric determination of ultra-trace cadmium in natural waters, Talanta 62 (2004) 437. [21] R. Khani, F. Shemirani, B. Majidi, Combination of dispersive liquideliquid microextraction and flame atomic absorption spectrometry for preconcentration and determination of copper in water samples, Desalination 266 (2011) 238. [22] Z.A. Alothman, E. Yilmaz, M. Habila, A. Shabaka, M. Soylak, Ligandless temperature-controlled ionic liquid-phase microextraction of lead(II) ion prior to its determination by FAAS, Microchim. Acta 180 (2013) 669. [23] D. Han, K.H. Row, Trends in liquid-phase microextraction,and its application to environmental and biological samples, Microchim. Acta 176 (2012) 1. [24] M. Baghdadi, F. Shemirani, Cold-induced aggregation microextraction: a novel sample preparation technique based on ionic liquids, Anal. Chim. Acta 613 (2008) 56. [25] J. Zhang, H.K. Lee, Headspace ionic liquid-based microdrop liquid-phase microextraction followed by microdrop thermal desorption-gas chromatographic analysis, Talanta 81 (2010) 537. [26] O. Sha, X. Zhu, Y. Feng, W. Ma, Aqueous two-phase based on ionic liquid liquid-liquid microextraction for simultaneous determination of five synthetic food colourants in different food samples by high-performance liquid chromatography, Food Chem. 174 (2015) 380. [27] P. Fern andez, C. Gonz alez, M.T. Pena, A.M. Carro, R.A. Lorenzo, A rapid ultrasound-assisted dispersive liquideliquid microextraction followed by ultra-performance liquid chromatography for the simultaneous determination of seven benzodiazepines in human plasma samples, Anal. Chim. Acta 767 (2013) 88. [28] M.B. Mahaveer, C. Wei-Shan, B. Hsin-Yu, L. Tzuen-Yeuan, F. Ming-Ren, Determination of 7-aminoflunitrazepam in urine by dispersive liquideliquid microextraction with liquid chromatographyeelectrospray-tandem mass spectrometry, Talanta 78 (2009) 618. [29] E. Yilmaz, M. Soylak, Development a novel supramolecular solvent microextraction procedure for copper in environmental samples and its determination by microsampling flame atomic absorption spectrometry, Talanta 126 (2014) 191. [30] P. Berton, E.M. Martinis, L.D. Martinez, R.G. Wuilloud, Selective determination of inorganic cobalt in nutritional supplements by ultrasound-assisted temperature-controlled ionic liquid dispersive liquid phase microextraction and electrothermal atomic absorption spectrometry, Anal. Chim. Acta 713 (2012) 56. [31] P.G. Jessop, D.J. Heldebrant, X. Li, C.A. Eckert, C.L. Liotta, Green chemistry: reversible nonpolar-to-polar solvent, Nature 436 (2005) 1102. [32] L. Phan, D. Chiu, D.J. Heldebrant, H. Huttenhower, E. John, X. Li, P. Pollet, R. Wang, C.A. Eckert, C.L. Liotta, P.G. Jessop, Switchable solvents consisting of amidine/alcohol or guanidine/alcohol mixtures, Ind. Eng. Chem. Res. 47 (2008) 539. [33] P.G. Jessop, S.M. Mercer, D.J. Heldebrant, CO2-triggered switchable solvents, surfactants, and other materials, Energy. Environ. Sci. 5 (2012) 7240. [34] T. Arthur, J.R. Harjani, L. Phan, P.G. Jessop, P.V. Hodson, Effects-driven chemical design: the acute toxicity of CO2-triggered switchable surfactants to rainbow trout can be predicted from octanol-water partition coefficients, Green. Chem. 14 (2012) 357. [35] L. Phan, J.R. Andreatta, L.K. Horvey, C.F. Edie, A.L. Luco, A. Mirchandani, D.J. Darensbourg, P.G. Jessop, Switchable-polarity solvents prepared with a single liquid component, J. Org. Chem. 73 (2008) 127. [36] X. Su, M.F. Cunningham, P.G. Jessop, Switchable viscosity triggered by CO2 using smart worm-like micelles, Chem. Commun. 49 (2013) 2655. [37] S.M. Mercer, T. Robert, D.V. Dixon, C.S. Chen, Z. Ghoshouni, J.R. Harjani, S. Jahangiri, G.H. Peslherbe, P.G. Jessop, Design, synthesis, and solution

[38] [39]

[40] [41]

[42]

[43]

[44] [45]

[46]

[47]

[48]

[49]

[50]

[51]

[52]

[53]

[54]

[55]

behaviour of small polyamines as switchable water additives, Green. Chem. 14 (2012) 832. J.R. Vanderveen, J. Durelle, P.G. Jessop, Design and evaluation of switchablehydrophilicity solvents, Green. Chem. 16 (2014) 1187. A.J. Reynolds, T.V. Verheyen, S.B. Adeloju, E. Meuleman, P. Feron, Towards commercial scale postcombustion capture of CO2 with monoethanolamine solvent: key considerations for solvent management and environmental impacts, Environ. Sci. Technol. 46 (2012) 3643. M.L. Stone, C. Rae, F.F. Stewart, A.D. Wilson, Switchable polarity solvents as draw solutes for forward osmosis, Desalination 312 (2013) 124. Y. Du, B. Schuur, C. Samorì, E. Tagliavini, D.W.F. Brilman, Secondary amines as switchable solvents for lipid extraction from non-broken microalgae, Bioresour. Technol. 149 (2013) 253. M. Soylak, L. Elci, M. Dogan, Determination of some trace metals in dialysis solutions by atomic absorption spectrometry after preconcentration, Anal. Lett. 26 (1993) 1997. M. Chamsaz, M. Eftekhari, A. Atarodi, S. Asadpour, M. Ariani, Preconcentration procedure using vortex agitator system for determination of trace levels of cadmium by flame atomic absorption spectrometry, J. Braz. Chem. Soc. 23 (2012) 1630. s, R. Lucena, S. C rcel, Use of switchable G. Lasarte-Aragone ardenas, M. Valca solvents in the microextraction context, Talanta 131 (2015) 645. I.G. Dakova, V.A. Dakov, M. Karadjov, I.B. Karadjova, Cu(II)-imprinted copolymer microparticles: effect of the porogen solvents on particle size, morphology and sorption efficiency, Bulg. Chem. Commun. 47 (2015) 296. M. Soylak, O. Ercan, Selective separation and preconcentration of Copper(II) in environmental samples by the solid phase extraction on multi-walled carbon nanotubes, J. Hazard. Mater. 168 (2009) 1527. F. Sabermahani, N.M. Mahani, Extraction and preconcentration of Pb(II) from water and soil samples using modified activated carbon, Iran. Chem. Commun. 3 (2015) 57. A. Duran, M. Soylak, S.A. Tuncel, Poly(vinyl pyridine-poly ethylene glycol methacrylate-ethylene glycol dimethacrylate) beads for heavy metal removal, J. Hazard. Mater. 155 (2008) 114. M. Ghaedi, K. Niknam, K. Taheri, H. Hosseinian, M. Soylak, Flame atomic absorption spectrometric determination of copper, zinc and manganese after solid phase extraction using 2,6-dichlorophenyl-3,3-bis(indolyl)methane loaded on amberlite XAD-16, Food Chem. Toxicol. 48 (2010) 891. S. Mahpishanian, F. Shemirani, Preconcentration procedure using in situ solvent formation microextraction in the presence of ionic liquid for cadmium determination in saline samples by flame atomic absorption spectrometry, Talanta 82 (2010) 471. J.S. Carletto, R.M. Luciano, G.C. Bedendo, E. Carasek, Simple hollow fiber renewal liquid membrane extraction method for pre-concentration of Cd(II) in environmental samples and detection by flame atomic absorption spectrometry, Anal. Chim. Acta 638 (2009) 45. J.J. Ma, X. Du, J.W. Zhang, J.C. Li, L.Z. Wang, Ultrasound-assisted emulsificationemicroextraction combined with flame atomic absorption spectrometry for determination of trace cadmium in water samples, Talanta 80 (2009) 980. J. Chen, K.C. Teo, Determination of cadmium, copper, lead and zinc in water samples by flame atomic absorption spectrometry after cloud point extraction, Anal. Chim. Acta 450 (2001) 215. D. Citak, M. Tuzen, M. Soylak, Simultaneous coprecipitation of lead, cobalt, copper, cadmium, iron and nickel in food samples with zirconium(IV) hydroxide prior to their flame atomic absorption spectrometric determination, Food Chem. Toxicol. 47 (2009) 2302. M. Tuzen, K.O. Saygi, M. Soylak, Solid phase extraction of heavy metal ions in environmental samples on multiwalled carbon nanotubes, J. Hazard. Mater. 152 (2008) 632.