Speciation of selenium(IV) and selenium(VI) using coupled ion chromatography - Hydride generation atomic absorption spectrometry

A simple method was developed to speciate inorganic Se in the mu g L-1 range using coupled ion chromatography-hydride generation atomic absorption spectrometry. Because of the differences in toxicity and adsorption behavior, determination of the redox states selenite, Se(IV), and selenate, Se(VI), is important. We used anion exchange chromatography to separate Se(IV) and Se(VI) based on differences in retention times. Samples were then mixed with concentrated HCI and passed through a 130 degrees C sand bath to reduce Se(VI) to Se(IV) for Se determination as the hydride. Detection limits were 0.68 mu g L-1 for Se(IV) and 0.55 mu g L-1 for Se(VI). Spiking of actual sample solutions with Se(IV) and Se(VI) showed the procedure to be accurate for solutions with Se(IV)/Se(VI) ratios ranging from 1:4 to 4:1. Average recovery was 93.1% for Se(IV) and 108% for Se(VI). The technique was used to determine Se(IV) and Se(Vi) in deionized water and actual and synthetic irrigation waters.