Selective Determination of Selenium(IV) and Selenium(Vl) in Waste Water by Graphite Furnace AAS after Reductive Coprecipitation on Tellurium Collector by Ascorbic Acid, Tin(II) Chloride and Hydrazinium Sulfate

Abstract

Selective determination of selenium(IV) and selenium(VI) in waste water by graphite furnace atomic absorption spectrometry (GFAAS) was developed. The method is based on the reductive coprecipitation of selenium(IV) by L-ascorbic acid or tin(II) chloride and of selenium(VI) by hydrazinium sulfate on a tellurium collector, followed by GFAAS. The ppb levels of selenium(IV) and selenium(VI) were quantitatively coprecipitated with 50 - 500 ug amounts of tellurium collector in 100 ml (1 M HCl). The selective separation of selenium(IV) from selenium(VI) could be achieved in the presence of 0.2-4.0 g of L-ascorbic acid or the optimized amount of tin(II) chloride (molar ratio [SnCl₂-2H₂O]/[Te(IV)]=50). The proposed methods were successfully applied to real waste-water samples and the standard reference material of river water (JAC0032). The detection limit (3σ) was about 0.5 ppb of selenium of the water sample.