Determination of arsenic and selenium species in groundwater and soil extracts by ion chromatography coupled to inductively coupled plasma mass spectrometry

A procedure for the separation and determination of the five arsenic species As(III), As(V), monomethylarsonic acid, dimethylarsinic acid and arsenobetain by ion chromatography coupled to inductively coupled plasma mass spectrometry under the use of anion exchange is described. It has been successfully applied to the analysis of groundwater and extracts of contaminated soils. No interference of 40Ar, 35Cl and 75As was observed when natural water samples were analyzed. The procedure shows good repeatability and accuracy in addition to easy handling. Detection limits for the arsenic species are in the range 0.4¯0.8 mug l-1. A detection limit of 4 mug l-1 was obtained for the selenium species. Interference by Cl- up to concentrations of 400 mg l-1 can be neglected. The influence of several parameters (eluent concentration, amount of methanol in the mobile phase, flow rate) has been studied so as to optimize the best chromatographic conditions. The procedure has prospects for environmental biomonitoring using a sensitive and efficient determination of arsenic and selenium species, as shown for groundwater samples spiked at the 50 mug l-1 level.