Speciation of inorganic selenium using flow injection hydride generation atomic fluorescence spectrometry

Two methods based on flow injection atomic fluorescence have been developed in order to speciate Se as Se-IV-Se-VI. Both methods use hydride generation of Se-IV with atomic fluorescence detection as the derivatization-detection step. In the first method, two sample plugs are injected simultaneously in series, so that the first plug passes straight to the detector to determine Se-IV. The second plug passes through a focused microwave device where Se-VI is reduced to Se-IV prior to its conversion into the hydride. The Se-VI content is then given as the difference between the two results. In the second method a mini-column is used to retain both the Se species; Se-IV and Se-VI are then eluted sequentially with formic and hydrochloric acids, respectively. The columns can be used for preconcentration of the analytes as well as for sampling. Both methods show exceptional sensitivity [limits of detection (3s) of 0.04 mu g l(-1)] and wide linear range up to 50 mu g l(-1), with excellent linearity (r(2)=0.999), and reproducibility (relative standard deviation < 5%). The methods have been used in an intercomparison exercise for the Measurements and Testing Programme and have been applied to the determination of the analytes in tap water and haemodialysis samples.