Fluorescence derivatization of amino acids with 4-(5′,6′-dimethoxybenzothiazolyl)phenylisothiocyanate in liquid chromatography Original Research Article

4-(5′,6′-Dimethoxybenzothiazolyl)phenylisothiocyanate is shown to be a highly sensitive Edman-type fluorescence derivatization reagent for amino acids in liquid chromatography. The reagent reacted with 20 tested amino acids in a basic medium to give the corresponding thiocarbamoyl derivatives. The derivatives were converted in an acidic medium to the thiohydantoin derivatives which were separated by reversed-phase chromatography within 80 min by gradient elution using mixtures of acetonitrile, tetrahydrofuran and 0.1 M triethylamine–acetic acid buffer (pH 5.0), and were detected by fluorimetry. The detection limits (signal-to-noise ratio=3) for amino acids were 18–33 fmol in a 20 μl injection volume.