Solid Phase Extraction of Copper , Cadmium and Lead Using Amberlite XAD-4 Resin Functionalized with 2-Hydroxybenzaldehyde Thiosemicarbazone and its Application on Green Tea Leaves

Abstract

A new chelating resin, 2-hydroxybenzaldehyde thiosemicarbazone loaded XAD-4, was synthesized and characterized by FT-IR and elemental analyses. The synthesized resin was used for solid phase extraction (SPE) and preconcentration of Cu 2+ , Cd 2+ , and Pb 2+ from aqueous solution, where the metal ions were subsequently determined by graphite furnace atomic absorption spectrometry (GF-AAS). The optimum pH for preconcentration and separation of these metal ions was found to be 6.00. Optimum flow rate for quantitative sorption of the metal ions on functionalized resin was found to be 1 mL/min whereas 2 M nitric acid was selected as the eluent for quantitative release of the three metal ions from the resin column. The maximum adsorption capacity of the functionalized resin was found to be 3.5, 6.1, and 11.26 mg/g for Cu 2+ , Cd 2+ , and Pb 2+ , respectively. The detection limits for these metal ions are 0.87, 0.95, and 1.09 µg/L, respectively and limits of quantification are 1.12, 1.29, and 1.16 µg/L, respectively. The sorption half time (t1/2) was found to be 6 min for Cu 2+ and Cd 2+ and 8 min for Pb 2+ . Tolerance limits for various foreign electrolytes have also been investigated. A high preconcentration factor (~100) and low relative standard deviation ≤ 5% (n=3) values were obtained. Under optimum conditions, recovery of all metal ions was found to be nearly quantitative. The validation of the procedure was carried out by analysis of certified reference materials. The functionalized resin is highly stable and can be reused more than 100 times. The newly developed method was applied to the separation, preconcentration and determination of Cu 2+ , Cd 2+ , and Pb 2+ in tea leaves