Inorganic and organic selenium compound speciation with coupled HPLC-MW-HG-AFS

Coupling between high-performance liquid chromatography, microwave-induced reduction, hydride generation and atomic fluorescence spectrometry (HPLC–MW–HG–AFS) has been used for selenium speciation. The concentrations of a redox mixture (HCl solution of KBr and KBrO3 aqueous solutions) used for both destruction of organic matter and reduction of the selenium species have been optimized, as well as the concentration of NaBH4 in the hydride generation step. Chromatographic separation of selenocysteine, selenite and selenate took place in 15 min, employing a polymer-based strong anion-exchange column. Calibrations with correlation coefficients r > 0.998 were obtained for the three compounds at concentrations between 0.5 and 10 µg l−1. Detection limits for selenite, selenocysteine (SeCys) and selenate were 0.2, 0.3 and 0.5 µg l−1, respectively. The coupling has been tested with spiked water samples (tapwater and seawater), obtaining recoveries in the range 94–104%.