A highly sensitive and precise radioenzymatic assay for plasma epinephrine and norepinephrine

A modification of the procedures for simultaneous radiometric determinations of plasma epinephrine (E) and norepinephrine (NE) was developed. High performance liquid chromatography (HPLC) is excellently suited to separate the radioactive products of the enzymatic methylation of catecholamines. The time-saving procedure shows significant advantages as against the conventional method of isolating normetanephrine and metanephrine by thin layer chromatography. The high sensitivity (detection limit = 1 pg), specifity, and good precision (cv = 6%) of this assay are demonstrated.