2-(5-hydrazinocarbonyl-2-oxazolyl)-5,6-dimethoxybenzothiazole as a precolumn fluorescence derivatization reagent for carboxylic acids in high-performance liquid chromatography and its application to the assay of fatty acids in human serum.

A unique acid hydrazide, 2-(5-hydrazinocarbonyl-2-oxazolyl)-5,6-dimethoxybenzothia zole, that is characterized by the benzothiazole structure conjugated to an oxazoline moiety was synthesized, and its applicability as a precolumn derivatization reagent for carboxylic acids in HPLC was examined in view of sensitivity and separability. The sensitivity of the hydrazide for carboxylic acids was determined using lauric acid to be 0.1 pmol (per 10-microliters injection volume) at a signal-to-noise ratio of 3. The reagent allowed rapid assays of carboxylic acids within 20 min with satisfactory separability. The method was applied to the determination of fatty acids in human sera from healthy volunteers as well as from patients with diabetes or thyroid dysfunction.