Single-step method for derivatization of dopamine and some related compounds in aqueous media for gas chromatography

The present report describes a single-step method for derivatization of dopamine and several structurally related compounds, either a catecholic or a monophenolic amine, acid, alcohol or glycol present in aqueous solutions. Also, nanogram levels of these compounds may be assayed by gas chromatography with electron-capture detection following derivatization. For the determination of optimum reaction conditions, aqueous solutions of either [14C]dopamine or [3H]norepinephrine were reacted with the derivatization agent, heptafluorobutyryl chloride. A mass spectrum of the derivative of dopamine confirmed the formation of triheptafluorobutyryl dopamine. To determine the sensitivity and specificity of the derivatization method, a number of biological samples from rats and humans were analyzed for dopamine and 3,4-dihydroxyphenylacetic acid. The urinary analyses showed that conjugation may be the major metabolic pathway for dopamine and 3,4-dihydroxyphenylacetic acid in rats as well as in humans. The present method should prove convenient to determine the urinary sulfate conjugate of 3,4-dihydroxyphenylacetic acid, a non-invasive indicator of central nervous system dopaminergic activity, and other catecholamine metabolites of clinical interest.