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 oxidation-hydride generation atomic absorption spectrometry coupled system has been developed for the determination of arsenite, arsenate, dimethylarsinate (DMA), monomethylarsonate (MMA), arsenobetaine and arsenocholine in environmental samples. An anionic cartridge placed before the HPLC anionic column (Hamilton PRP-X100) quantitatively retains anionic species such as arsenite, arsenate, MMA and DMA but not cationic species which are separated and quantitatively determined after microwave-K2S2O8 decomposition. The anionic species can be separated and determined quantitatively by removing the anionic cartridge from the system and introducing water instead of K2S2O8 solution. Detection limits of between 0.3 and 0.9 ng were achieved for all species. A conversion efficiency close to 100% was achieved for the species tested, working with a microwave oven power of 700 W and 5% K2S2O8 oxidizing solution.