Arsenic speciation in serum of uraemic patients based on liquid chromatography with hydride generation atomic absorption spectrometry and on-line UV photo-oxidation digestion

An on-line method was developed for the speciation of arsenic species in human serum, including monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenobetaine (AsB) and arsenocholine (AsC). The method is based on cation-exchange liquid chromatography (LC) separation, UV-photo-oxidation for sample digestion and continuous hydride generation (HG) atomic absorption spectrometry (AAS) for the measurement of arsenic in the LC eluent. By developing the technique of argon segmented flow in the post-column eluent, an substantial improvement in chromatographic resolution for the separation of these four arsenic species was obtained. The LC separation, photo-oxidation, hydride generation and AAS measurement could be completed on-line within 10 min. The detection limits were 1.0, 1.3, 1.5 and 1.4 mu g/l of arsenic for MMA, DMA, AsB and AsC, in serum respectively. The concentration of the 4 species was determined in serum samples of patients with chronic renal insufficiency. Only AsB and DMA were significantly detected by the present method. The main part of arsenic in human serum is AsB. No MMA, AsC and inorganic arsenic were detected in these 6 samples.