NormalReferenceIntervalsfor Free Catecholaminesand Their Acid Metabolitesin 24-h UrinesfromChildren,as Determinedby Liquid

We used two methods of reversed-phase liquid chromatogra-phy with amperometnc detection, one for assay of unconju-gated norepinephrine, epinephnne, and dopamine in urine, the other for determination of unconjugated vanillylmandelic acid and homovanillic acid. The catecholamines were ex-tracted from urine by passage through a weak-cation ex-change 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. AdditIonal Keyphrases: reversed-phase chromatography ‘ nor