Simultaneous speciation of inorganic selenium and antimony in water samples by electrothermal vaporization inductively coupled plasma mass spectrometry following selective cloud point extraction.

A new method was developed for the simultaneous speciation of inorganic selenium and antimony in water by electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) following selective cloud point extraction (CPE). The method is based on the fact that Se(IV) and Sb(III) could form complexes with diethyldithiocarbamate (DDTC) at pH 6.00, and the complexes were quantitatively extracted into the non-ionic surfactant-rich phase of octylphenoxypolyethoxyethanol (Triton X-114), whereas the Se(VI) and Sb(V) remained as free species in aqueous solutions. Sb(III) and Se(IV) in concentrate were determined by ETV-ICP-MS after proper disposal. The total Se and total Sb were determined by the same protocol after Se(VI) and Sb(V) were reduced by l-cysteine, and Se(VI) and Sb(V) concentrations were obtained by respectively subtracting Se(IV) and Sb(III) from the total Se and the total Sb. Under the optimized conditions, the limits of detection (LODs) were 0.05 microg L(-1) for Se(IV) and 0.03 microg L(-1) for Sb(III), the relative standard deviations (RSDs) were 3.5% for Se(IV) and 4.2% for Sb(III) (C=1.00 microg L(-1), n=5). The proposed method was applied to the speciation of inorganic selenium and antimony in different water samples with satisfactory results.