Speciation analysis of selenium in natural water using square-wave voltammetry after preconcentration on activated carbon

A simple, accurate, sensitive and selective method was described for rapid determination of ultra-trace quantities of selenium. Selenium(IV) was collected on activated carbon (AC) after reduction to elemental Se by l-ascorbic acid. The collected selenium was then dissolved by oxidation reaction with bromate in acidic media and was indirectly determined through the bromide formation using square-wave voltammetry (OSWV). The total amount of Se(IV) and Se(VI) was collected on AC after its reduction by hydrazine. Selenium in the range 0.01-20 μg L⁻¹ could be determined by this method. The method was used to the determination of Se(IV) and Se(VI) in natural water with satisfactory results.