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Free and sulphoconjugated catecholamine (CA) concentrations were measured in plasma using a fully automated and sensitive analyser equipped with a three-column system of high-performance liquid chromatography (HPLC). Although the free dopamine (DA) concentration has been below the detection limit of HPLC analysers thus far available, this new CA analyser can measure as little as 0.03 nmol/L. For the estimation of sulphoconjugated CA, we performed enzymatic deconjugation with arylsulphatase prior to HPLC analysis. The difference between free and total concentrations represents that of sulphoconjugated CA. The intraassay coefficient variation was less than 2.2% for free noradrenaline (NA) and adrenaline (A), 12.62% for free DA, and less than 4.3% for total A, and DA. These assays of free and sulphoconjugated CA are simple and can be performed routinely by a suitably equipped laboratory.
Yoshimura et al. (Mon,) studied this question.