Determination of inorganic selenium in KSC by electrophoretic capillary ion analysis

An assay to determine the amount of inorganic selenium in KSC has been developed using electrophoretic capillary ion analysis (CIA). Parameters which influence CIA separation such as the addition of an electroosmotic flow modifier, choice of electrolyte anions and the buffer'S pH are investigated. In the optimized system, selenate and slenite are separated in a buffer containing chromate, triethanolamine, and tetradecyltrimethylammonium bromide at pH 9.2. There is sufficient resolution to allow accurate quantification. 10 mg/L bromide is used as internal standard. Quantification is highly reproducible with a migration time RSD of 0.89% over 6 runs and a peak area RSD of 1.23%. The method is linear over two orders of magnitude. The detection limits of lower than 0.5 mg/L are attainable when the pressure injection (3.5 kPa) time is 10s. The selenite recovery (101%) is acceptable.