Determination of dopa, dopamine, dopac, epinephrine, norepinephrine, alpha-monofluoromethyldopa and alpha-difluoromethyldopa in various tissues of mice and rats using reversed-phase ion-pair liquid chromatography with electrochemical detection.

A method for the determination of catecholic amino acids and amines by reversed-phase ion-pair high-performance liquid chromatography with electrochemical detection has been developed. B using octanesulfonic acid for ion pairing and by optimising ionic strength, pH and methanol concentration of the mobile phase, separation was achieved of 3,4-dihydroxyphenylalanine (DOPA), 3,4-dihydroxyphenylacetic acid (DOPAC), norepinephrine (NE), epinephrine (EPI), and dopamine (DA). Alpha-Difluoromethyldopa (DFMD) and alpha-monofluoromethyldopa (MFMD), two potent enzyme-activated irreversible inhibitors of aromatic amino acid decarboxylase were also separated from the natural catechols. Concentrations of catechols and inhibitors were measured in brains, hearts and kidneys of mice treated with small repeated doses of MFMD. The method has also been applied to the determination of catechols in other organs such as prostates and seminal vesicles of rats and in smaller tissues like mesenteric arteries. A semi-automated procedure making use of an automatic sample processor and a digital integrator permitted the analysis of as many as sixty samples per day.