DETERMINATION OF 6 ARSENIC SPECIES BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY HYDRIDE GENERATION ATOMIC-ABSORPTION SPECTROMETRY WITH ONLINE THERMOOXIDATION

Anion-exchange HPLC has been coupled to on-line thermo-oxidation and h ydride generation-atomic absorption spectrometry (HG-AAS) for the spec iation of As(V), As(III), MMA, DMA, AsB and AsC. The thermoreactor con sists of a loop of PTFE tubing dipped in a powdered-graphite oven heat ed to + 140-degrees-C. Samples and persulphate solution run together i nto the thermo-reactor. The thermo-oxidation conditions were optimized using a FIA system. The chromatographic and chemical parameters affec ting hydride generation efficiency were optimized. The overlap of the As(III) and AsB peaks made it necessary to determine AsB as the differ ence between absorbance in the presence and in the absence of thermo-o xidation. The thermo-conversion efficiencies were above 96%. Recoverie s were around 100% and detection limits below 1 ng. The proposed metho d is rapid, sensitive and precise (RSD about 5%), making it suitable f or on-line determination in environmental samples.