Determination of Trace Selenium in Groundwater by DRC-ICP-MS

Abstract

BACKGROUND Generally, the content of Se in groundwater is lower than 1μg/L. Mass interferences caused by polyatomic species and low ionization degree can seriously affect the accuracy for determination of trace and ultratrace Se in groundwater by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Moreover, the current detection limit is higher than required for practical purposes. OBJECTIVES To establish DRC-ICP-MS method for determination of trace selenium in groundwater. METHODS Ethanol was used as a signal enhancer, methane was used as a reaction gas. The factors that affect different mass determination, including methane flow, ethanol content, atomizing gas flow rate, low mass interception (RPq), RF generator (Rf) power, ion residence time were discussed and optimized. RESULTS Ethanol can increase response values, whereas ethanol and methane can obviously eliminate the mass spectrometry interference. Under the optimized conditions, except 74Se, calibration curves show a good relationship (R > 0.9996). The method detection limits are 0.02-0.03μg/L, the relative standard deviation (RSD, n=5) is lower than 2%, and the average spiked recovery is 95.7%. CONCLUSIONS The method has simple pretreatment and single equipment, which can meet the requirements for determination of trace selenium in large quantities of groundwater.

Keywords

• groundwater
• trace se
• dynamic reaction cell
• inductively coupled plasma-mass spectrometry
• ethanol
• methane