The Determination Of Arsenic, Lead, Cadmium By Atomic Spectrometry In Foods And Drinking Water

The determination of arsenic,lead,cadmium with atomic spectrometry in foods and drinking water were investigated thoroughly.A method was developed for the determination of total arsenic in foods using flow injection(FI) on-line adsorption coupled with hydride generation atomic fluorescence spectrometry(HG-AFS) by cigarette filter as the sorbent material.After reducing As(â…¤) to As(â…¢) by using L-cysteine,the determination of total As was achieved through on-line formation and retention of the pyrrolidine dithiocarbamate arsenic complex(As(â…¢)-PDC) on the cigarette filter which was packed in the preconcentration column and total arsenic was determined by HG-AFS.The analytes were eluted with 1.68 mol L^-1 HCl from the sorbent material.With consumption of 22 mL of the sample solution,an enrichment factor of 25.6 was obtained.The detection limits(3SD) and the precisions(RSD) in foods were ranged from 2.5 to 9.9 ng g^-1 and 1.1 to 2.2%,respectively.A typical room temperature ionic liquid,1-butyl-3-methylimidazolium hexafluorophosphate([C₄mim][PF₆]),was used as a novel solvent which replaced traditional volatile organic solvents to study extraction of Pb²⁺ in foods and water samples.Diethyldithiocarbamate(DDTC) was employed as a metal chelator to form neutral complexes with Pb²⁺ and the complex was extracted from aqueous phase to [C₄mim][PF₆].After back-extracted into aqueous phase with 2.0 mol L^-1 HNO₃,the Pb concentration was detected by graphite furnace atomic absorption spectrometry. The detection limits(3SD) and the relative standard deviation for 11 replicate extractions of 2 ng mL^-1 Pb²⁺ were found to be 0.04 ng mL^-1 and 2.5%,respectively. The ionic liquid can be recycled for reuse in liquid/liquid extraction of Pb²⁺.A new hydrophobic task specific ionic liquid(TSIL) which was prepared by appending MBT substituted alkyl groups to imidazoles and combining with PF₆^-anion,was employed to extract Cd²⁺ from foods and water samples.In basic medium, Cd²⁺ formed a complex with TSIL and then was extracted into ionic liquid phase. After back-extracted into aqueous phase with 0.24 mol L^-1 HCl,the Cd concentration was detected by flame atomic absorption spectrometry.The detection limits(3SD) and the relative standard deviation for 11 replicate extractions of 10 ng mL^-1 Cd²⁺ were found to be 0.15 ng mL^-1 and 1.96%,respectively.