Phytoremediation of Lead from Soil by Lepidium ...

International Journal of Scientific Research in Knowledge (IJSRK), 1(6), pp. 140-147, 2013 Available online at http://www.ijsrpub.com/ijsrk ISSN: 2322-4541; ©2013 IJSRPUB http://dx.doi.org/10.12983/ijsrk-2013-p140-147

Full Length Research Paper Spectrophotometric Determination of Trace Zn(II) with Phenanthraquinone Monophenyl Thiosemicarbazone Following Homogeneous Liquid-Liquid Extraction in the Water-Acetic Acid-Chloroform Ternary Solvent System Ali Mazloomifar*, Maliheh Ahadi Department of Chemistry, Shahre Ray Branch, Islamic Azad University, Tehran, Iran *Corresponding Author: [email protected] Received 12 April 2013; Accepted 08 May 2013

Abstract. A selective and simple method for separation and preconcentration of Zn2+ ions was developed by homogeneous liquid-liquid extraction method based on the pH dependent phase separation phenomenon was studied in the water-acetic acidchloroform ternary solvent system. Phenanthraquinone monophenyl thiosemicarbazone (PPT) was investigated as a suitable selective complexing ligand for Zn2+ ions. Under optimum conditions the extraction efficiency % of Zn2+ was 96.2% and concentration factor 800-fold (i.e. 50µL the sedimented phase was produced from 40 mL of the aqueous phase). The proposed homogeneous liquid-liquid extraction method was applied as a preconcentration method for the spectrophotometric determination of Zn2+ with PPT. The calibration graph was linear over the range 0.20 – 1.20 ng mL-1. The relative standard deviation (RSD%) for the central value of calibration curve was (1.56%) for 10 determinations and the detection limit was 0.06 ng mL-1. The proposed method was applied for the extraction and determination of Zn 2+ in natural water samples with satisfactory results. Key words: Zinc, phenanthraquinone monophenyl thiosemicarbazone, Homogeneous liquid-liquid extraction.

extraction (Sudo, 1996; Takahashi, 1999, 2001; Igarashi, 2000). Recently, homogeneous liquid-liquid extraction was successfully utilized for the extraction of some organic and inorganic analytes (Oshite, 2001; Akiyama, 2004; Ghiasvand, 2004, 2005). This method extract the solute in a homogeneous solution into the very small sedimented phase formed from the solution by the phase-separation phenomenon. The objective of the present study is to apply a laboratory synthesized reagent ie (PPT) for the preconcentration and separation of Zn-PPT chelate into very small chloroform using homogeneous liquid liquid extraction in a water-acetic acid-chloroform ternary solvent system.

1. INTRODUCTION Zinc is an essential trace element for humans, animals, plants and microorganisms. The Zinc content in humans is 2-4g (Welz, 1999). Zinc plays many fundamental roles in cell replications, gene expression and in the metabolism of nucleic acid and different proteins (Das, 1990). The sensitive, selective and rapid methods for the determination of Zinc are in great demand. Atomic absorption spectrometry (AAS) (Taher, 2000), graphite furnace atomic absorption spectrometry (GF-AAS) (Alvarado et al., 1991), neutron activation analysis (NAA) (Garg et al., 1993), inductively coupled plasma-atomic emission spectrometry (ICP-AES) (Asfaw and Wibetoe, 2005), inductively coupled plasma-mass spectrometry (ICP-MS) (Forrer et al., 2001), direct current plasma atomic emission spectrometry (DC-PAES), X-ray fluorescence are widely applied to the determination of metals at trace level (Petersson et al., 1993; Igarashi et al., 2000). Preconcentration technique allows the improvement of detection limit as well as the selectivity of the method. Homogeneous liquidliquid extraction is a simple and powerful preconcentration method. That reduces the extraction time, disposal costs, consumption and exposure to the organic solvents. The ternary component solvent system and the perfluorinated surfactant system are the two usual modes of homogeneous liquid-liquid

2. EXPERIMENTAL 2.1. Apparatus The absorption spectra were recorded on a unico 4802 double beam spectrophotometer and pH measurements were made with a model F-11 Horiba pH- meter. A Hettich EBA-8 centrifuge was used for centrifugation.

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Mazloomifar and Ahadi Spectrophotometric Determination of Trace Zn(II) with Phenanthraquinone Monophenyl Thiosemicarbazone Following Homogeneous Liquid-Liquid Extraction in the Water-Acetic Acid-Chloroform Ternary Solvent System

(0.334 g, 2 mmol in ethanol) was added to (0.416 g, 2 mmol) 9,10-phenanthraquinone dissolved in the least amount of glacial acetic acid. The resulting solution was boiled under reflux for 1h. The PPT crystals were filtered off, washed with ethanol, recrystallized from absolute ethanol and finally dried in a vacuum desiccators over anhydrous CaCl2. A standard solution (1000 µg mL-1) was prepared by dissolving an appropriate amount of PPT in chloroform. Working solutions were prepared by appropriate dilution of the stock solution.

2.2. Reagents and solutions All reagents were of analytical reagent grade from Merck. All organic solvents were of HPLC grade from Merck or Aldrich. A stock solution of Zn2+ ions (1000 µg mL-1 ) was prepared by dissolving an appropriate amount of Zn(NO3)2.6H2O and diluted with doubly distilled water. The phenanthraquinone monophenyl thiosemicarbazone (PPT) (Scheme1) was synthesized using a previously reported method (Akl, 2006). A hot solution of 4-phenyl thiosemicarbazide

Scheme 1: Structure of phenanthraquinone monophenyl thiosemicarbazone (PPT).

2.3. Analytical Procedure 3. RESULTS AND DISCUSSION A sample solution (40 mL) containing 10 ng of Zn2+ ions was placed in a 50 mL cylindrical glass vial fitted with a plastic cap, 0.2 mL of PPT solution and 4.5 mL of acetic acid were separately added. After gentle mixing, 5.1 mL of 10 mol L-1 sodium hydroxide solution was added. The mixture was allowed to stand for 5 min in the room temperature and then centrifuged for 5 min at 2000 rpm. The sedimented phase (50µL) was removed using a 100 µL microsyringe and transferred into a spectrophotometer cell and diluted to 1 mL with chloroform. The Zn2+ concentration then was determinated at 523 nm against a blank.

3.1. Absorption spectra The absorption spectra of PPT reagent and Zn-PPT complex are given in figure 1. As can be seen, the absorption spectrum of PPT is characteristic as having two maxima at 415 nm and 449 nm (curve a) which may be attributed to the presence of keto-enol or thioenol equlibrium (Scheme 2). The spectrum of Zn-PPT complex in chloroform phase (curve b) reflects the presence of a single chelate exhibiting a maximum absorption at 523 nm, at which the reagent dose no absorb appreciably.

Scheme 2: Keto-enol or thio-enol equilibrium

effect appeared above pH=11 when a high concentration of sodium hydroxide was added. As a result, an increase in the volume of the sedimented chloroform phase was observed. In the pH range of 511 the optimum sedimented chloroform phase becomes a constant volume (50µL).

3.2. Effect of pH on phase separation The relationship between the pH and volume of the sedimented phase is shown in figure 2. The phase separation phenomena, which depend on the pH was observed in the pH range of 5-11. The salting-out

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International Journal of Scientific Research in Knowledge (IJSRK), 1(6), pp. 140-147, 2013

Fig. 1: Absorption spectra of a: The PPT reagent in the chloroform, b :Zn-PPT chelate in the chloroform.

Fig. 2: The relationship between pH and volume of sedimented phase. (In the final solution: [Zn2+]=0.25 ng mL-1, [CH3COOH] =10% v/v, [PPT]=5.0 ng mL-1, pH= 8.5 ).

thus obtaining the desired preconcentration. pH plays an unique role on metal-chelate formation and subsequent extraction. The relationship between the pH and the absorption is shown in figure 3. As a result, The absorption was maximal in the pH range of 7.5-9.0. Thus, pH value of 8.5 was used for this work.

3.3. Effect of the pH on absorption The separation of metal ions by homogeneous liquidliquid extraction involves prior formation of a complex with sufficient hydrophobicity to be extracted into the small volume of sediment phase;

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Fig. 3: Effect of pH on the absorbance of Zn(II). (In the final solution: [Zn2+]=0.25 ng mL-1 , [CH3COOH] =10% v/v , [PPT]=5.0 ng mL-1 ).

volume range of added chloroform 200-300 µL. The curve in figure did not pass through the origin, because small amounts of chloroform dissolve in water. The concentration factor (the volume ratio (va/vs) of the aqueous phase (va) and sedimented phase (vs) ) was 800, that is, 50 µL of the chloroform phase was produced from 40mL of the aqueous solution. Hence, 200 µL of added chloroform was selected.

3.4. Microvolume of the sedimented chloroform phase In this extraction method, the concentration factor is strongly dependent on the volume of the sedimented chloroform phase. The relationship between the volume of added chloroform and the volume of the sedimented phase is shown in figure 4. As a result, the volume of sedimented (i.e. 50 µL) was constant in the

Figure 4: The relationship between the chloroform volume and the volume of sedimented phase. (In the final solution: [Zn2+]=0.25 ng mL-1 , [CH3COOH] =10% v/v , [PPT]=5.0 ng mL-1, pH= 8.5 ).

that the extraction percent was quantitative for PPT concentrations higher than 3.0 ng mL-1. Thus, a concentration of 5.0 ng mL-1 was used for further studies.

3.5. Effect of PPT concentration The effect of the concentration of PPT on the absorption is shown in figure 5. The results showed

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Figure 5: Effect of the concentration of PPT on the absorption (In the final solution: [Zn2+]=0.25 ng mL-1 , [CH3COOH] =10% v/v , pH= 8.5 ).

The limit of detection, defined as CL =3 SB / m (where CL, SB and m are the limit of detection, standard deviation of the blank and slope of the calibration graph, respectively), was 0.06 ng mL-1. The relative standard deviation (RSD) for ten replicate measurements of 0.25 ng mL-1 Zn (II) was 1.56%.

3.6. Calibration graph and the relative standard deviation Table 1 summarizes the analytical characteristics of the optimized method, including linear range, limit of detection, reproducibility and concentration factor.

Table 1. Analytical characteristics of proposed method

determination of Zn(II) ions in two different natural water samples. The results are given in Table 3.

3.7. Interferences In order to investigate the selective extraction and determination of Zn2+ ions using PPT from binary mixtures with various metal ions, and aliquot of a solution containing 1.0 ng of Zn2+ ions and different amounts of other cations was taken and the recommended procedure was followed. An ion was considered to interfere when its presence produced a variation in the absorbance of the sample of more than 5%. This increment of absorbance was evaluated at wavelength 523 nm (corresponding to maximum absorption of Zn complex). The results are summarized in Table 2. The results show that the Zn2+ ions in the binary mixtures were extracted almost completely, even in the presence of up to 8 ng of some cations.

4. CONCLUSION Homogeneous liquid-liquid extraction utilizes a phase separation phenomenon from the homogenous solution and makes it possible to rapidly and powerfully concentrate analytes. A phenanthraquinon monophenyl thiosemicarbazone was synthesized and investigated as a suitable selective complexing ligand for Zn2+ ions. A simple and efficient method for the selective separation and preconcentration of Zn2+ ions using Homogeneous liquid-liquid extraction was developed. The proposed Homogeneous liquid-liquid extraction method for the extraction and determination of Zn2+ ions is simple, selective and sensitive. The proposed procedure successfully applied to separation, preconcentration and determination of zinc in real samples.

3.8. Application to Samples To assess the applicability of the method to real samples, it was applied to the extraction and

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Mazloomifar and Ahadi Spectrophotometric Determination of Trace Zn(II) with Phenanthraquinone Monophenyl Thiosemicarbazone Following Homogeneous Liquid-Liquid Extraction in the Water-Acetic Acid-Chloroform Ternary Solvent System Table 2: Separation of Zn2+ ions from binary mixtures using PPT

(In the final solution: [Zn2+]=0.25 ng mL-1 , [CH3COOH] =10% v/v , [PPT]=5.0 ng mL-1, pH= 8.5 ).

Table 3: Determination of Zn2+ in real samples .

(In the final solution: [Zn2+]=0.25 ng mL-1, [CH3COOH] =10% v/v , [PPT]=5.0 ng mL-1, pH= 8.5 ).

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ACKNOWLEDGMENT The author thanks the research council at the University of Islamic Azad , Shahre Ray Branch for financial support. REFERENCES Akiyama R, Takagai Y, Igarashi S. (2004). Determination of lower sub ppt levels of environmental analytes using high-powered concentration system and high-performance liquid chromatography with fluorescence detection. Analyst,129: 396-397. Akl MA (2006). The Use of Phenanthraquinone Monophenyl Thiosemicarbazone for Preconcentration, Ion Flotation and Spectrometric Determination of Zinc(II) in Human Biofluids and Pharmaceutical Samples. Bull. Korean Chem. Soc., 27: 725-732. Alvarado J, Moreno R, Cristiano AR (1991). Determination of Cd, Cr, Cu, Pb and Zn in

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Dr. Ali Mazloomifar is an Assistant Professor in analytical chemistry at Shahre Rey Branch, Islamic Azad university, Iran. Dr. Mazloomifar received his Ph.D in analytical chemistry (chromatography) from Islamic Azad university, Iran in 2002. He obtained degree in Master of science in analytical chemistry in 1998 from Tabriz university. He received his first degree in applied chemistry from BuAli Sina university, Hemedan, Iran in 1996. Dr. Mazloomifar has published several scientific articles related to separation field.

Maliheh Ahadi is a PhD student in analytical chemistry at Islamic Azad University, Science & Research branch, Tehran, Iran. She received her M.S. degree from Payamenor University, Mashhad, Iran in analytical chemistry.

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Phytoremediation of Lead from Soil by Lepidium ... - IJSRPUB.com

Phytoremediation of Lead from Soil by Lepidium ... - IJSRPUB.com

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