Modified fluorometric method for determining plasma catecholamines.

Plasma catecholamines were fluorometrically determined by a modification of the standard alumina-trihydroxyindole method in which radioactive tracer catecholamines are used to follow the chromatographic behavior of the endogenous catecholamines on alumina. This modification permits appropriate fluorometry of that portion of the eluate with the highest concentration of catecholamines, because incomplete elution of the total endogenous catecholamines can be corrected by use of the isotope recovery data. Additionally, a low column blank was obtained; this method of blank preparation may have obviated some of the known difficulties associated with unoxidized and incomplete plasma blanks that have traditionally been used.