ARSENIC SPECIATION IN SERUM OF UREMIC PATIENTS BASED ON LIQUID-CHROMATOGRAPHY WITH HYDRIDE GENERATION ATOMIC-ABSORPTION SPECTROMETRY AND ONLINE UV PHOTOOXIDATION DIGESTION

An on-line method was developed for the speciation of arsenic species in human serum, including monomethylarsonic acid (MMA), dimethylarsini c 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 arse nic in the LC eluent. By developing the technique of argon segmented f low in the post-column eluent, an substantial improvement in chromatog raphic 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 detectio n limits were 1.0, 1.3, 1.5 and 1.4 mu g/l of arsenic for MMA, DMA, As B and AsC, in serum respectively. The concentration of the 4 species w as determined in serum samples of patients with chronic renal insuffic iency. Only AsB and DMA were significantly detected by the present met hod. The main part of arsenic in human serum is AsB. No MMA, AsC and i norganic arsenic were detected in these 6 samples.