Simultaneous determination of arsenic species and chromium(VI) by high-performance liquid chromatography–inductively coupled plasma-mass spectrometry

The simultaneous determination of As(III), As(V), monomethylarsenic acid (MMA), dimethylarsinic acid (DMA) and Cr(VI) in fresh water has been carried out by coupling an anion-exchange column to an inductively coupled plasma-mass spectrometer. Optimisation of chromatographic conditions led to baseline separation of signals from the five species in approximately 9 min using gradient elution. Detection limits were 0.02–0.05 μg As l−1 and 5.5 μg Cr l−1. Repeatability was 2–3% for arsenic species and higher, i.e., 8%, for Cr(VI) due to the higher background for this species. Arsenic species and hexavalent chromium stability in surface water samples was evaluated, and storage conditions were set to 1 day at 4°C in polyethylene flasks (without acidification) in order to avoid As(III)–As(V) conversions. The method was applied to the analysis of surface water.