Speciation measurements by HPLC-HGAAS of dimethylarsinic acid and arsenobetaine in three candidate lyophilized urine reference materials

Abstract

Speciation measurements of dimethylarsinic acid (DMA) and arsenobetaine (AsB) in three candidate lyophilized urine reference materials are described. The measurements were based on cation-exchange liquid chromatography coupled to hydride generation atomic absorption spectrometry with on-line digestion of the organic As species by alkaline persulfate solution aided by ultraviolet radiation. Arsenic concentrations as DMA were significantly different in the three samples. The mean values for the three samples were 4.1 ± 0.3, 55.3 ± 1.2 and 134.1 ± 1.5 µg l^–1, respectively. No significant differences in AsB concentrations were observed among the three samples. The mean As concentrations as AsB in the three samples were 17.4 ± 0.4, 17.7 ± 0.2 and 17.5 ± 0.3 µg l^–1, respectively. By off-line digestion of the urine samples, total As concentrations in the three materials were also obtained. The mean values were 23.4 ± 0.3, 76.6 ± 1.6 and 151.3 ± 1.8 µg l^–1, respectively. These results correlated well with the results obtained by neutron activation analysis in our laboratory (r = 0.999; p <0.0001).