DETERMINATION OF CATECHOLAMINES AND METHOXYCATECHOLAMINES EXCRETION PATTERNS IN PIG AND RAT URINE BY ION-EXCHANGE LIQUID-CHROMATOGRAPHY WITH ELECTROCHEMICAL DETECTION

A simplified liquid chromatographic method for the simultaneous determ ination of free or total catecholamines and methoxycatecholamines in r at and pig urine is presented. The extraction procedure involves a two -stage batch extraction, with successive adsorption on cation- (catech olamine elution) and anion-exchange columns (methoxycatecholamine elut ion). The column eluates are successively monitored by reversed-phase high-performance liquid chromatography (HPLC) with electrochemical det ection. The proportion of conjugates for each compound was assessed in both species, through the comparison of concentrations with or withou t hydrolysis pretreatment. Conjugates were found to account for a smal l fraction of total catecholamines and methoxycatecholamines excretion (0 to 35%). The free fraction of each compound was highly correlated with the total amount. Furthermore, the hydrolysis procedure leads to partial degradation of metanephrine (25%) and to the production of com pounds giving artefactual peaks. Thus, we do not recommend hydrolysis of rat and pig urines for catecholamine and methoxycatecholamine deter mination. (C) 1997 Elsevier Science B.V.