Normal reference intervals for free catecholamines and their acid metabolites in 24-h urines from children, as determined by liquid chromatography with amperometric detection.

We used two methods of reversed-phase liquid chromatography with amperometric detection, one for assay of unconjugated norepinephrine, epinephrine, and dopamine in urine, the other for determination of unconjugated vanillylmandelic acid and homovanillic acid. The catecholamines were extracted from urine by passage through a weak-cation exchange resin, then through alumina. Vanillylmandelic acid and homovanillic acid were isolated from urine by a two-step solvent-extraction procedure. The between-day CV was 5% for norepinephrine, 3% for epinephrine, 3% for dopamine, 4.5% for vanillylmandelic acid, and 6.4% for homovanillic acid. Reference ranges for these analytes in 76 children, ages 3-16 years, are reported.