ION-CHROMATOGRAPHIC DETERMINATION OF SELENITE AND SELENATE WITH SELENIUM-SPECIFIC DETECTION BY FLAME AND GRAPHITE-FURNACE ATOMIC-ABSORPTION SPECTROMETRY

An ion chromatographic method for the determination of selenite and selenate using both Zeeman-effect graphite furnace atomic absorption spectrometry (GFAAS) and Zeeman-effect flame atomic absorption spectrometry (FAAS) for selenium-specific detection is described. Different mobile phases were investigated (aqueous solutions of potassium hydrogenphthalate (KHP) of various pH and concentration; KHP solutions saturated with nickel hydroxide; aqueous solutions of nickel nitrate or nickel sulphate). The pH dependence of the retention times of selenite and selenate was determined. Interferences by sulphate and sulphite in the determination of selenite and selenate were studied with conventional conductivity and GFAAS detection. The absolute detection limits for liquid chromatography (LC)-GFAAS were found to be 1 ng Se for selenite and 0.6 ng Se for selenate when a 3 mM KHP solution saturated with NI(OH), was used as the mobile phase. LC-FAAS had an absolute detection limit of 8 ng Se for selenite and 11 ng Se for selenate. The LC-FAAS system was used to determine selenite and selenate in different solutions used for selenium supplementation of animals. The results obtained for the selenium compounds agreed with the total selenium determinations.