Low-level Selenium Determination

Introduction Selenium is an essential element to human health at low levels (2080 μg/L), but becomes toxic at elevated levels. Selenium exists in different forms that determine its toxicity and bioavailability. Current research is now focusing on the determination of individual selenium species or seleniumcontaining compounds. This can be done using ICP-MS as a selenium-specific detector for a chromatographic separation of the compounds. Since the critical levels of the individual compounds will be significantly less than the total selenium concentration, it is becoming more necessary to be able to make very low level selenium determinations. This application note discusses the use of the ELAN® Dynamic Reaction CellTM (DRCTM) ICP-MS for making low-level selenium determinations. With conventional quadrupole ICP-MS, the most abundant isotope of selenium (80Se) cannot be used for the determination due to the interfering Ar2 + dimer from the argon plasma which occurs at the same mass-to-charge ratio (m/z). As a result, selenium is normally determined using the 82Se isotope, which is only 8.7% abundant. This limits the detection capability for selenium to the 0.510 μg/L range by conventional ICP-MS. Using the ELAN DRC ICP-MS, this limitation can be overcome by removing the Ar2 + interference. This allows the most abundant isotope of selenium, 80Se, to be used in the determination, resulting in detection limits that are on the order of a thousand times better than those obtainable by conventional ICP-MS.