SELENIUM SPECIATION BY COUPLING VESICLE MEDIATED HPLC WITH OFF-LINE ETAAS AND ONLINE FOCUSED MICROWAVE DIGESTION HG-AAS DETECTION

A novel High Performance Liquid Chromatography (HPLC) method for the s eparation of selenium species with specific detection by off-line Elec trothermal Atomization Atomic Absorption Spectrometry (ETAAS) or on-li ne focused microwave digestion (MW) Hydride Generation Atomic Absorpti on Spectrometry (HG-AAS) is described. Vesicular mobile phases of the cationic surfactant didodecyldimethylammonium bromide (DDAB) have been evaluated for the liquid chromatographic separation of inorganic sele nium (selenite and selenate) and different selenoaminoacids (selenocys tine, selenomethionine and selenoethionine) on a C-18 reversed-phase c olumn modified by DDAB molecules. The effects of different parameters (pH, buffer and vesicle concentrations) of the mobile phase on the ret ention times have been determined. The detection limit for selenium wi th the proposed off-line HPLC-ETAAS method has been found to be 5 mu g /L of Se. The detection limit using HPLC-''on line'' focused microwave digestion-HG-AAS has been found to be 1 mu g/L of Se, with a precisio n (repeatability) better than +/- 5%. The latter proved to be an excep tional on-line real-time chromatographic detector for selenium speciat ion purposes.