Mikihiko Saito

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.

Abstract A unique acid hydrazide, 2-(5-hydrazinocarbonyl-2-oxazolyl)-5,6-dimethoxybenzothiazole, that is characterized by the benzothiazole structure conjugated to an oxazoline moiety was synthesized, and its applicability as a precolumn derivation 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-μ1 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.

2-(5-hydrazinocarbonyl-2-thienyl)-5,6-methylenedioxybenzofuran and 2-(5-hydrazinocarbonyl-2-furyl)-5,6-methylenedioxybenzofuran as novel fluorescence derivatisation reagents for carboxylic acids in liquid chromatography

Abstract The new acid hydrazides, 2-(5-hydrazinocarbonyl-2-thienyl)-5,6-methylenedioxybenzofuran (TMBH) and 2-(5-hydrazin-ocarbonyl-2-furyl)-5, 6-methylenedioxybenzofuran (FMBH), were synthesized as precolumn fluorescence derivatisation reagents for carboxylic acids in liquid chromatography. These compounds readily react with carboxylic acids in the presence of a coupling reagent under mild conditions in aqueous solution to give fluorescent derivatives. The detection limits of lauric acid were both 0.1 pmol per 10 μl injection volume at a signal-to-noise ratio of 3. The methods in which these compounds are used were applied to the assay of a standard mixture of prostaglandins (25 μM) and prostaglandins in a human seminal fluid.

2-Amino-4,5-ethylenedioxyphenol as fluorescence derivatization reagent for aromatic aldehydes in liquid chromatography

Abstract 2-Amino-4,5-ethylenedioxyphenol was found to be useful as a precolumn fluorescence derivatization reagent for aromatic aldehydes in liquid chromatography. The reagent reacts selectively with the aldehydes in two steps: first, heating (100°C) for 45 min in methanol solution in the presence of dicyclohexylcarbodiimide; secondly, standing for more than 1 min at room temperature after acidification. The fluorescent product from 4-hydroxybenzaldehyde is shown to be 2-(4-hydroxyphenyl)-5,6-ethylenedioxybenzoxazole. The fluorescent derivatives of aromatic aldehydes can be separated by reversed-phase chromatography and their detection limits (S/N = 3) are 5–10 pmol on column.