Simultaneous speciation and determination of arsenic, chromium and cadmium in water samples by high performance liquid chromatography with inductively coupled plasma mass spectrometry

The simultaneous separation and determination of As(III), As(V), monomethylarsenic acid (MMA), dimethylarsenic acid (DMA), Cr(III), Cr(VI) and Cd(II) in water samples have been carried out by anion exchange liquid chromatography with inductively coupled plasma mass spectrometry. Ethylenediaminetetraacetic acid was used to form negatively charged complexes with Cr(III) and Cd(II). For achieving the optimum chromatographic conditions, the effects of competing ion type, mobile phase concentration and pH on speciation have been investigated. By compromising among analysis time, chromatographic resolution and sensitivity, 40 mM ammonium nitrate at pH 8.6 has been selected as the mobile phase for real sample applications. The baseline separation of all the target species has been achieved under isocratic elution conditions. Under the optimized conditions, the limit of detection was in the range of 0.07–0.12 μg L⁻¹ for the various species. The proposed method was applied to the determination of the target species in surface water and drinking water samples. Arsenate was the dominant arsenic species in all the tested samples. Neither MMA nor DMA was detected in real water samples. The recoveries for spikes of individual species in water samples tested ranged from 88% to 116%.