Determination of different oxidation states of arsenic and selenium by inductively coupled plasma-atomic emission spectrometry with ion chromatography

Recent regulation in Japan requires more sensitive trace analysis methods for the determination of arsenic and selenium and their oxidation states As(III) and (V), Se(IV) and (VI). The hydride generation (HG) technique is usually used in combination with AAS and ICP-AES to increase sensitivity. However, hydrochloric acid is mostly used to acidify the sample solution in HG. Isobaric interferences due to chlorine-related species cause mass spectral problems when the same solution is used for the determination of these elements by ICP-MS. In this study, different oxidation states of As and Se were determined by coupling ion chromatography (IC) to an ICP-AES instrument. An HG technique was used to introduce test samples into the ICP. Nitric acid was employed to acidify the samples for HG. The concentrations of acid and base were kept as low as possible to reduce contamination. The formation of As and Se hydrides could be achieved without HCl, if the concentrations of acid and alkaline solutions were optimized. However, HCl was necessary for additional reduction of Se(VI) to Se(IV).