Sensitive determination of three arsenic species in water by ion exclusion chromatography-hydride generation-inductively coupled plasma mass spectrometry

Abstract

A sensitive and robust speciation method for arsenic in water is described. The separation of arsenate (As ^V ), arsenite (As ^III ), and monomethylarsonic acid (MMA) was performed using an ion exclusion column packed with a sulfonated polystyrene resin and using dilute trifluoroacetic acid at pH 2.1 as the mobile phase. The hydride generation method was used to improve sensitivity and to eliminate interference from chloride ions. The analysis time per sample was 18 min but could be shortened to 9 min by using a column switching method. The detection limits for the arsenic species were 1.1 pg ml ^–1 for As ^V , 0.5 pg ml ^–1 for As ^III , and 0.5 pg ml ^–1 for MMA, with an injection volume of 50 µl. The relative standard deviations of five replicates of a standard containing 1 ng ml ^–1 As of each species ranged from 0.8 to 2.8%. The method was validated by analyzing reference water samples.