DETERMINATION OF SELENIUM SPECIES IN SEAWATER BY FLOW-INJECTION HYDRIDE GENERATION IN-SITU TRAPPING FOLLOWED BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

In this study, Se-IV was determined in seawater by flow injection hydr ide generation, trapping within the graphite furnace, followed by elec trothermal atomic absorption spectrometry. The optimized protocol perm itted a preconcentration factor of 1000 lowering the detection limit o f Se-IV in seawater to about 1.5 ng l(-1) for a 25 mi sample volume, B ecause this technique is specific to Se-IV, various physico-chemical t reatments leading to the conversion of other chemical forms into Se-IV were investigated. Thermal and UV irradiation treatments of seawater samples in acidic or basic medium permitted the conversion of Se-II-se lenomethionine and Se-VI to Se-IV. Based on the different responses of selenium species towards the photochemical treatments, an operational speciation model of selenium species in seawater is proposed. Accordi ng to our analytical protocol, 21 ng l(-1) Se-VI, 10 ng l(-1) Se-IV an d 13 ng l(-1) organic Se-II species mere determined in a coastal surfa ce seawater collected near Brest.