Determination of plasma catecholamines by means of radioenzymatic labelling and high pressure liquid chromatographic separation.

0.05 ml plasma samples are incubated with 3H-S-adenosylmethionine and catechol-O-methyl-transferase. The resulting methodoxy derivatives are extracted, the extracts separated by high pressure liquid chromatography and the metanephrine fractions collected. Evaluation is performed by liquid scintillation counting of radioactivity in the respective fractions. The following performance criteria are presented: precision, accuracy, detectability (40 pg/ml for adrenaline and noradrenaline, 130 pg/ml for dopamine), linearity and day-by-day variation. Comparison with a standard method shows an excellent correlation for adrenaline and noradrenaline.