Differential assay for urinary catecholamines by use of liquid chromatography with fluorescence detection.

I describe a relatively simple and rapid procedure for quantitative analysis for unconjugated urinary norepinephrine, epinephrine, and dopamine. Catecholamines are isolated from urine on a carboxylic acid ion-exchange resin (Bio-Rex 70) and eluted with 0.8 mol/L boric acid. The eluates are assayed for the individual catecholamines by "high-performance" liquid chromatography with an octadecylsilane reversed-phase column and 10 mmol/L perchloric acid-acetonitrile (99/1) as the mobile phase. The catecholamines are detected by measuring their intrinsic fluorescence on excitation at 200 nm. The method is highly reproducible, the coefficient of variation for normal concentrations in urine being 4.4% for norepinephrine, 8.8% for epinephrine, and 4.8% for dopamine. Moreover, it appears to be practically free of interference by drugs or endogenous compounds in urine. The range of catecholamine concentrations found in 143 hypertensive patients agrees well with previous studies.