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Polymeric reducinq agents, such as polymeric borohydride resins, can be successfully utilized in both the pre-and oost-column modes, online, a t ambient temperatures, in real-time, for the selective chemical reduction o f a large number of aldehydes. Other classes of carbonyl derivatives, such as ketones, esters, amides, etc., are totally unreactive under these same polymeric reduction conditions. This particular reducing agent i s fully compatible with conventional reversed phase HPLC columns and mobile phases, such as methanol/water, ethanol/water, and acetonitrile/ water, in varying proportions. The approach t o selective detection in HPLC described here utilizes conventional UV-VIS detection following pre-or post-column reductions that occur on-line. Alternative detection methods could just as readily be utilized. Overall reactions are rapid, quantitative, reproducible, and highly selective. In certain cases, i t i s possible t o realize improved detection limits as a result of aldehyde reductions. Difference chromatography or changes in detector responses for unresolved reactant and product can be used t o denote reactions that have occurred on the original analyte(s) of interest. Polymeric reduction columns can be slurry packed a t f a i r l y low pressures, and they are stable a t elevated HPLC back pressures for prolonged periods of time and use. The use of polymeric reagents in HPLC i s a totally qeneral approach to improved specificity, selectivity, and detection limits in a l l types of organic and inorganic analyses.

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