Speciation of toxicologically important arsenic species in human serum by liquid chromatography–hydride generation atomic absorption spectrometry

Abstract

An on-line method was developed for the speciation of trivalent and pentavalent inorganic arsenic (As), monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) in serum. The method is based on HPLC separation of As species and continuous HGAAS for the measurement of As in the HPLC eluate. Three types of HPLC system were evaluated in order to find a method that was applicable to serum samples: reversed-phase ion-pair chromatography, polymer-based anion-exchange chromatography and silica-based anion-exchange chromatography. As the last-named appeared more suitable, the analytical conditions were optimized, and a procedure is proposed for the speciation of As species in serum. Phosphate buffer of pH 4.5 at a concentration of 30 mmol l^–1 was used as the mobile phase. Serum samples were adjusted to the same pH as that of the mobile phase before injecting them onto the column. The detection limits were 0.49, 0.44, 0.92 and 0.40 µg l^–1 for As^III, As^V, MMA and DMA in serum, respectively. The HPLC separation, hydride generation and AAS measurement could be completed on-line within 10 min. The method was applied to the speciation of As in the serum of patients with chronic renal disease. The only As species that could be measured in the serum of the patients was DMA.