Critical evaluation of the application of photochemical vapor generation in analytical atomic spectrometry

Chemical vapor generation (CVG) is a widely adopted sample introduction method for analytical atomic spectrometry. Nonvolatile precursors (usually ionic, metallic or organometallic species) can be transferred from the condensed phase to the gas phase, yielding the advantages of efficient matrix separation, high analyte transport efficiency, high selectivity, simple instrumentation, and ease of automation. Hydride generation enjoys the greatest popularity as a consequence of its ease of implementation, fast reaction and high yield; but photo-CVG, a newly emerging research field in analytical chemistry, may provide a powerful alternative to conventional CVG due to its simplicity, versatility and cost effectiveness. Although photocatalytic pre-reduction has been used for a number of years, the most attractive aspect of this newly emerging area is the direct generation of volatile species using photochemical reactions. Recent studies undertaken with flow through and batch reactors employing low molecular weight organic acids as photochemical agents are highlighted in this study for such systems as mercury and selenium, as well as reaction mechanisms considered for these processes. Discussion is focused on recent advances in photo-CVG, which we believe will become the subject of intensive future research initiatives.