PRECOLUMN DERIVATIZATION OF RETINOIC ACID FOR LIQUID-CHROMATOGRAPHY WITH FLUORESCENCE AND COULOMETRIC DETECTION

Derivatization of the carboxyl function of retinoic acid by fluorescent or electroactive reagents prior to liquid chromatography was studied. Ferrocenylethylamine was synthesized and could be coupled to retinoic acid. The coupling reaction involved activation by diphenylphosphinyl chloride. The reaction was carried out at ambient temperature in 50 min with a yield of ca. 95%. The derivative can be detected by coulometric reduction (+ 100 mV) after on-line coulometric oxidation (+ 400 mV). The limit of detection was 1 pmol of derivative on-column, injected in a volume of 10 mu l, but the limit of quantification was 10 pmol of retinoic acid.