Determination of metanephrine and normetanephrine by high-performance liquid chromatography with electrochemical detector and its diagnostic application for pheochromocytoma

Objective To establish high-performance liquid chromatography with electrochemical detector(HPLC-ECD) method for the determination for metanephrine and normetanephrine in 24 h urine, and provide a superior test for the diagnostic of pheochromocytomas over plasma/urine catecholamine.Methods MCX solid-phase cartridge was used for extraction of metanephrine and normetanephrine,HPLC-ECD was used for their measurements.The intra-assay CVs,interassay CVs and recoveries of metanephrine and normetanephrine were also calculated.104 hypertensive patients without pheochromocytomas and 5 pheochromocytomas patients were selected in this study.The concentrations of metanephrine and normetanephrine were compared with the plasma and 24h urinary catecholamines concentrations.Results The intra-assay CV,inter-assay CV and recovery of metanephrine were 5.9%, 7.5%,91.1% respectively;the intra-assay CV,inter-assay CV and recovery of normetanephrine were 6.3%,6.6%,88.5%,respectively.The MN,NMN,plasma CA and urine CA of all pheochromocytomas patients were positive.MN and NMN were negative in controls,while plasma CA and urine CA are false positive in 15 patients and 14 patients in controls,respectively.Conclusions The study establish a fast and accurate method for quantification of metanephrine and normetanephrine in 24 h urine by HPLC-ECD.These findings also prove that it is the best biochemical assays for pheochromocytomas at present.