A sensitive method for determination of conjugated catecholamines in blood plasma

Conjugated catecholamines in blood plasma of blood donors were determined from the difference between the total and the free catecholamines. Total catecholamines were measured after complete hydrolysis of the conjugated amines (heating of acidified samples for 40 min at 95 degrees C). Free catecholamines were determined in untreated plasma. Determinations were performed radioenzymatically. We combined and modified the procedures of Peuler & Johnson (1977) Life Sci 21, 625-636) and Da Prada & Zürcher (1976) Life Sci 19, 1161-1174). The resulting method was less laborious and cheaper.