Determination of selenite and selenate in environmental waters using ion chromatography-mass spectrometry | Poster Board #1811

Selenium is an important element in environmental research due to the narrow window differentiating its presence as an essential trace element and its toxic effect upon exposure. Selenium is often found in the inorganic forms selenite and selenate in environmental samples, and the toxicity of selenium compounds greatly depends on its speciation. Consequently, selenium in environmental samples should be determined not only as total selenium, but also as species-specific when possible. There is a regulatory need to reduce selenium contamination of environmental waters. These efforts should therefore include steps to investigate the speciation of selenium during the removal process when treating environmental waters.
We developed a method to measure the concentration of selenite and selenate in environmental waters by coupling ion chromatography with mass spectrometry (IC-MS). Selenite and selenate are separated from other common anions in environmental water by a high-capacity anion exchange column in 20 minutes and are then detected by coupling a conductivity detector (CD) and a single quadrupole mass spectrometer (MS) detector in series.
The IC-MS method offers significant advantages over IC-CD methods in terms of sensitivity and selectivity. Coupling MS with CD takes advantage of the strengths of each detector; MS detection offers high sensitivity, and CD detection offers detection across a wide linear range. The limits of detection of selenite and selenate using IC-MS were 4 µg/L and 2 µg/L, respectively. This method was applied to wastewater, river water and lake water samples. The recovery of selenium species in environmental water that was spiked with known standards was 90-105%. With minimal sample preparation and the ability to use reagent free eluent preparation, this method can be easily and broadly applied to the screening of environmental water samples that might be contaminated with selenium.