Urinary free norepinephrine and dopamine determined by reverse-phase high-pressure liquid chromatography.

We used reverse-phase high-pressure liquid chromatography to measure free norepinephrine and dopamine simultaneously in human urine. Samples were treated with alumina, and the catecholamine(s) then eluted from it were directly injected onto a reverse-phase column (octadecyl-silica stationary phase), with 0.17 mol/liter acetic acid as the mobile phase and ultraviolet detection at 280 nm. The assay detects concentrations in urine as low as 5 mug/liter. Assay of 24-h urines (n = 10) gave within-run and day-to-day coefficients of variation of 3.7 and 4.7% for norepinephrine, and 2.6 and 3.5% for dopamine, respectively. Comparison studies with the traditional trihydroxyindole fluorometric method showed the liquid-chromatographic procedure to be more precise and subject to less interference. This relatively rapid procedure for urinary free norepinephrine and dopamine provides an efficient, reproducible method, readily adaptable to routine clinical use.