ONLINE MICROWAVE OXIDATION FOR THE DETERMINATION OF ORGANOARSENIC COMPOUNDS BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY HYDRIDE GENERATION ATOMIC-ABSORPTION SPECTROMETRY

An on-line high-performance liquid chromatography (HPLC)-microwave oxi dation-hydride generation atomic absorption spectrometry coupled syste m has been developed for the determination of arsenite, arsenate, dime thylarsinate (DMA), monomethylarsonate (MMA), arsenobetaine and arseno choline in environmental samples. An anionic cartridge placed before t he HPLC anionic column (Hamilton PRP-X100) quantitatively retains anio nic species such as arsenite, arsenate, MMA and DMA but not cationic s pecies which are separated and quantitatively determined after microwa ve-K2S2O8 decomposition. The anionic species can be separated and dete rmined quantitatively by removing the anionic cartridge from the syste m and introducing water instead of K2S2O8 solution. Detection limits o f between 0.3 and 0.9 ng were achieved for all species. A conversion e fficiency close to 100% was achieved for the species tested, working w ith a microwave oven power of 700 W and 5% K2S2O8 oxidizing solution.