Preconcentration and separation of inorganic selenium species on activated alumina

A simple and convenient method has been developed for the speciation of inorganic selenium in aqueous solutions using alumina microcolumn. Both Se(IV) and Se(VI) are retained on the microcolumn in a widely pH range of solution. The successive gradient elution of preconcentrated species with ammonia solution allows to differentiate between them. Se(VI) and Se(IV) were eluted with 1 ml of 1 mol l−1 NH3 and 6 ml of 4 mol l−1 NH3, respectively, and determined by graphite furnace atomic absorption spectrometry. The detection limit for Se(VI) is 0.80 μg ml−1 and for Se(IV) 49 ng l−1. The method has been applied to the speciation of inorganic selenium in natural water samples.