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

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