A critical review on photochemical conversions in flow analysis

•Critical review of coupling photochemical processes to flow analysis.•Discussion of flow approaches and design of flow-through photoreators.•General overview of the applications with tables highlighting the main aspects.•Quantitative and partial analyte conversions, fractionation and speciation analysis.•Discussion on miniaturization, reagentless procedures, and in-line waste treatment.

Photochemical conversions are cost-effective and environmental friendly processes that require mild experimental conditions and avoid generation of highly acidic wastes. Treated samples are then compatible with most of the analytical techniques. These characteristics become more relevant when the photoconversions are accomplished to flow analysis, thus allowing exploitation of incomplete reactions, the effective use of the photogenerated unstable radicals and in-line sample treatment. Decreasing of reagent consumption and waste generation, sample processing in a closed environment, and improvement of efficiency of the photochemical processes are other inherent advantages. These aspects are critically reviewed in this article, which emphasizes applications to fractionation and speciation analysis, photo-induced luminescence, miniaturization, and in-line waste treatment. Design of flow-through photochemical cells, use of auxiliary reagents in homogeneous and heterogeneous media, and configurations of flow manifolds are also discussed.

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