Arsenic speciation based on ion exchange high-performance liquid chromatography hyphenated with hydride generation atomic fluorescence and on-line UVphoto oxidation

An on-line method capable of the separation of arsenic species was develope d for the speciation of arsenite As(III), arsenate As(V), monomethylarsenic (MMA) and dimethylarsenic acid (DMA) in biological samples. The method is based on the combination of high-performance liquid chromatograph (HPLC) fo r separation, UV photo oxidation for sample digestion and hydride generatio n atomic fluorescence spectrometry (HGAFS) for sensitive detection. The bes t separation results were, obtained with an anion-exchange AS11 column prot ected by an AG11 guard column, and gradient elution with NaH2PO4 and water as mobile phase. The on-line UV photo oxidation with 1.5% K2S2O8 in 0.2 mol L-1 NaOH in an 8 m PTFE coil for 40 s ensures the digestion of organoarsen ic compounds. Detection limits for the four species were in the range of 0. 11-0.15 ng (20 muL injected). Procedures were validated by analysis of the certified reference materials GBW09103 freeze-dried human urine and the res ults were in good agreement with the certified values of total arsenic conc entration. The method has been successfully applied to speciation studies o f blood arsenic species with no need of sample pretreatment. Speciation of arsenic in blood samples collected from two patients after the ingestion of realgar-containing drug reveals slight increase of arsenite and DMA, resul ting from the digestion of realgar.