ONLINE FOCUSED MICROWAVE DIGESTION HYDRIDE GENERATION OF INORGANIC AND ORGANIC SELENIUM - TOTAL DETERMINATION AND INORGANIC SELENIUM SPECIATION BY ATOMIC-ABSORPTION SPECTROMETRY

An on-line FIA pretreatment with HBr/KBrO3, assisted by on-line focuse d microwave-induced digestion, has been coupled with hydride generatio n-atomic absorption spectrometry (HG-AAS) for final detection for tota l selenium determination. This total selenium determination is virtual ly independent of the different Se species investigated (selenite, sel enate, selenomethionine, selenoethionine and selenocystine). Detection limits of 0.8 mu g l(-1) of Se can be achieved by AAS with precisions better than 5%. This continuous flow system for selenium determinatio n allows a high sample throughput (about 30 samples h(-1) can be analy zed) in which high automation can be achieved and constitutes a conven ient real-time continuous detector for the different selenocompounds t ested. Direct non-chromatographic speciation of inorganic selenium (se lenite and selenate in their mixtures) is demonstrated by simple on-of f operation of the focused microwaves connected in the flow system. Va lidation of this simple on-line FIA system has been carried out by ana lyzing total Se recovered from spiked tap waters and by speciating mix tures of Se(IV) and Se(VI) spiked to the same samples. The fast conver sion of Se compounds into volatile selenium could be considered as a s ort of specific ''general'' detector for Se compounds which can be ext remely useful for Se speciation by hybrid chromatographic techniques.