Spectrophotometric determination of trace amounts of selenium(IV) by catalytic kinetic method

A spectrophotometric method for the determination of selenium(IV) is described, based on the selenium(IV)-catalyzed oxidation of methyl blue with KBrO3 in nitric acid medium. As the redox reaction proceeds, the blue colour of the dye is decolourized. LogA(0)/A shows a good linear relationship with the amount of selenium. The detection range of the method is 0-5 mug dm(-3) with sensitivity of 0.3527 mug dm(-3). The system is selective as most of the cations, viz, copper, potassium, iron, etc. can be tolerated during the determination of Se(IV). The method has been used to determine Se(IV) in Chinese herbal drugs.