3,4-Dimethoxybenzylamine as a sensitive pre-column fluorescence derivatization reagent for the determination of serotonin in human platelet-poor plasma

3,4-Dimethoxybenzylamine is shown to be a highly sensitive pre-column fluorescence derivatization reagent for the determination of serotonin in plasma by high-performance liquid chromatography. The reagent reacts selectively with 5-hydroxyindoles including serotonin in slightly alkaline media in the presence of potassium hexacyanoferrate(III) to give highly fluorescent derivatives. The derivatives of six standard 5-hydroxyindoles (5-hydroxytryptophan, 5-hydroxyindole-3-acetic acid, serotonin, 5-hydroxyindole-3-acetamide, N-acetyl-5-bydroxytryptamine and 5-hydroxytryptophol) are separated within 18 min by isocratic elution using acetonitrile-10 mM phosphate buffer (pH 6.0)-50 mM 1-hexanesulfonic acid on a Wakosil II 5C18RS reversed-phase column. The detection limits (signal-to-noise ratio=3) for the indoles were 1.0-5.7 fmol in a 100-mu l injection volume. The method was applied to the measurement of serotonin in human platelet-poor plasma.