3-O-Methyldopamine (3-O-Methoxytyramine) Interferes with the Internal Standard 3,4-Dihydroxybenzylamine in a Plasma Catecholamine HPLC Method

摘要

Plasma catecholamines are routinely assayed for the detection of pheochromocytoma and in clinical trials evaluating hemodynamic function in intensive care patients (1). HPLC combined with electrochemical detection is widely applied for the quantification of plasma catecholamines(2). We use a commercially available method for plasma catecholamine measurement (Chromsystems), including a pretreatment step for plasma samples that uses the relative nonspecific absorption of analytes onto Al2O3. Isocratic separation is then performed on a reversed-phase C18 column. Assay conditions include a 0.8 mL/min flow rate and a mobile phase containing salts, methanol, and an ion-pairing reagent. Quantification is performed with an L 3500 electrochemical detector (Recipe) at a potential of +500 mV. 3,4-Dihydroxybenzylamine (DHBA) is used as the internal standard.We observed an interference with the internal standard in patients taking part in a clinical study in our intensive care unit. Evaluation of the case histories revealed that these patients have received dopamine intravenously before blood …