Selective retention of catecholamines and their derivatives reversed-phase ion-pair partition chromatography

Abstract

Some possibilities are described to improve the separation between catechoamines and their corresponding metanephrines in reversed-phase ion-pair partition chromatography. The retention of amines can be influenced by the perchlorate concentration of the mobile phase, while the retention of acidic metalolites is governed by the pH of the mobile phase. Nevertheless, a separation between the catecholamines and their corresponding metanephrines cannot be achieved by optimizing these mobile phase parameters. A decrease in the temperature of the chromatographic system leads to an improvement in the separation betweeen dopamine and 3-methoxytyramine; however, adrenaline and noradrenaline are not separated from metanephrine and normetanephrine, respectively, and the chromatographic efficiency decreases. Addition of boric acid to the mobile phase results in a selective decrease in the retention of compounds with a catechol function, the magnitude of this effect depending on the mobile phase pH. Applying this “boric acid effect” it is possible to obtain a complete and rapid (within about 9 min) of the catecholamines, their corresponding metanephrines, the acidic metabolites homovanillic acid and 3,4-dihydroxyphenylacetic acid and the neutral metabolite 3-methoxy-4-hydroxyphenyl-ethylene glycol.