Speciation of arsenical species by anion-exchange and ion-pair reversed-phase liquid chromatography

Summary Speciation and quantitative analysis of arsenical compounds are performed by using high-performance liquid chromatography (HPLC) with direct UV detection. Ion chromatography has been used to separate mixtures of arsenical compounds (arsenite, MMA, DMA, arsenate) on an anion-exchange column using phosphate buffer (1 mmol/l, pH=5.3) as eluent. Ion -pair reversed-phase chromatography has been investigated to resolve mixtures of arsenite, arsenate, MMA, DMA, arsenobetaine and arsenocholine on an octadecyl-bonded silica column using water as mobile phase (pH=7.3) and tetrabutylammonium cation as ion-pairing reagent. The influence of several parameters (pH, the ion-pairing reagent concentration or the amount of methanol in the mobile phase) has been studied to determine the best chromatographic conditions.