DETERMINATION OF ARSENIC SPECIATION BY LIQUID-CHROMATOGRAPHY HYDRIDE GENERATION INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION-SPECTROMETRY WITH ONLINE UV PHOTOOXIDATION

The determination is described of the six arsenic species arsenite, arsenate, monomethylarsonate (MMA), dimethylarsinate (DMA), arsenobetaine and arsenocholine by hydride generation inductively coupled plasma atomic emission spectrometry after liquid chromatographic separation and on-line photooxidation. An anion-exchange polymer-based column is used for separation. The details of the photoreactor designed to transform arsenobetaine and arsenocholine into simpler species that can be reduced are presented. The reducing conditions to obtain the arsine from arsenate (as the final product of the photooxidation process) are optimized. The overall assembly is presented and using the optimized operating conditions the quality parameters (detection limits, precision and accuracy) for all the arsenic species are reported. These parameters for arsenite, arsenate, MMA and DMA are compared with those obtained without photooxidation. The introduction of a new step on-line in the coupling does not produce any loss of quality of information or a significant increase in analysis time.