An Automated Technic for Separate Fluorometric Measurement of Epinephrine and Norepinephrine in Urine

Abstract

To meet the greatly increased clinical demands for measurement of catecholamines in urine, a partially automated method was developed for separate and direct measurement of epinephrine (E) and norepinephrine (NE). Catecholamine extraction was facilitated by mechanical shaking in batches, and subsequent analysis of the trihydroxyindole derivatives of E and NE was controlled and recorded using an in-stream automated technic. Measurement of E was obtained at pH 3.5 using ascorbic acid stabilization; measurement of NE was obtained at pH 6.0 using thioglycolic acid stabilization. In equimolar amounts, NE contributed less than 5% of the fluorescence at pH 3.5, and E contributed no fluorescence at pH 6.0. Recovery of E and NE added to urine samples averaged 99% (range, 77 to 115%) and 97% (range, 60 to 120%), respectively. Reproducibility of results from the same urine specimen gave coefficients of variation of 5.5% for E and 7.9% for NE when analyzed on the same day, and 10.5% for E and 7.7% for NE when analyzed on separate days. The results of specimens analyzed by us and by other laboratories were comparable. Serious interference by drugs or other compounds was limited. The method greatly increases the number of specimens that can be analyzed, and the results are more accurate than those obtained by previous technics.