Speciation of inorganic selenium in environmental matrices by flow injection analysis-hydride generation-atomic fluorescence spectrometry. Comparison of off-line, pseudo on-line and on-line extraction and reduction methods

This paper reports several sensitive flow injection analysis-hydride generation-atomic fluorescence spectrometry (FIA-HG-AFS) analytical methods for inorganic selenium determination in waste waters and sewage sludge samples with different treatments: off-line, pseudo-on-line and on-line extraction and reduction to Se(IV). The on-line method, which combines Se extraction and Se reduction in a microwave oven (MW), requires the use of the standard additions method in real determinations. During the extraction steps no alteration of the Se oxidation states took place and it was possible to determine Se(IV) and total inorganic selenium. The proposed analytical methods were successfully applied to waste waters and sludge samples. Validation was performed by using reference materials (RM 602, 603 and Aquacheck 135, 143) and by recovery tests on spiked samples.