COUPLED PHOTOOXIDATION HYDRIDE AAS DETECTOR FOR THE HPLC OF ARSENIC COMPOUNDS

A widely applicable arsenic-specific detection system has been constructed for HPLC. The restricted range of compounds which can be detected by hydride generation atomic absorption spectroscopy (AAS) has been overcome by the incorporation of a simple low-power ultraviolet irradiation stage. The detector employs an on-line persulfate-mediated photooxidation prior to hydride generation, atomization, and measurement by AAS. The system has been shown to respond to arsenite, arsenate, dimethylarsinate, methylarsonate, arsenobetaine, arsenocholine, o- and p-arsanilate, phenylarsonate, and tetramethylarsonium ions. Confirmation of peak identity is enhanced by comparison of peak areas with and without photooxidation. Absolute detection limits (3 sigma) for the system are typically ca. 50 pg of arsenic corresponding to 0.3 mug of As/L using a 166-muL injection. Reproducibilities lie within the range +/- 1.1-4.2%.