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

An ion chromatographic method for the determination of selenite and se lenate using both Zeeman-effect graphite furnace atomic absorption spe ctrometry (GFAAS) and Zeeman-effect flame atomic absorption spectromet ry (FAAS) for selenium-specific detection is described. Different mobi le phases were investigated (aqueous solutions of potassium hydrogenph thalate (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 se lenate was determined. Interferences by sulphate and sulphite in the d etermination of selenite and selenate were studied with conventional c onductivity and GFAAS detection. The absolute detection limits for liq uid chromatography (LC)-GFAAS were found to be 1 ng Se for selenite an d 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 lim it of 8 ng Se for selenite and 11 ng Se for selenate. The LC-FAAS syst em 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.