Catecholamine sulfates as internal standards in HPLC determinations of sulfoconjugated catecholamines in plasma and urine

Abstract

A method is described to measure catecholamine sulfates from human plasma and urine by isocratic reversed-hase high-performance liquid chromatography with electrochemical detection. For this measurement we use catecholamine 3-sulfate isomers as internal standards and determine the sulfoconjugates only after eliminating the catecholamines. Catecholamines that have previously been used as internal standards are shown to cause a significant overestimation (P < 0.05) of the catecholamine sulfates - by 10% to 25% and 20% to 42% in human plasma and urine, respectively. The detection limits (signal-to-noise ratio > 3) in plasma and urine samples were about 80 pmol/L for each analyte. The intra-assay and interassay CVs were <4.0% and 10.6% in human plasma and <6.6% and 12.8% in human urine, respectively. The calibration curves for all catecholamine sulfates in human plasma and urine were linear (r >0.96; P <0.001) over the respective concentration ranges of 0.1-100 nmol/L and 5-1000 nmol/L.