Radiotracer error-diagnostic investigation of selenium determination by hydride-generation atomic absorption spectrometry involving treatment with hydrogen peroxide and hydrochloric acid

The radiotracer technique was used to find out the sources of systematic errors of a hydride generation AAS procedure for the determination of selenium in wastewater and other environmental samples. The investigated procedure involves sample decomposition with a mixture of sulfuric acid and hydrogen peroxide, and reduction of Se(VI) to Se(IV) by boiling with 5 M hydrochloric acid. Satisfactory recoveries are obtained in the decomposition (99.7 +/- 2%), reduction 98 +/- 1%), and hydration (95 +/- 3%) steps. Serious errors can be introduced via the time-dependent back oxidation of Se(IV) to Se(VI) by the residual chlorine produced in the reduction step. Removal of the chlorine from the solution is necessary if the hydration does not follow the reduction step immediately. 10 references, 2 figures, 2 tables