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Endocrinology and Metabolism |
1 Department of Laboratory Medicine & Pathology, Mayo Clinic and Foundation, 200 First Street SW, Rochester, MN 55905.
aAuthor for correspondence. Fax 507-284-9758; e-mail singh.ravinder{at}mayo.edu.
Background: Quantification of plasma free metanephrines is usually accomplished by HPLC with electrochemical detection, but sample preparation is labor-intensive and time-consuming, run times are long, and interfering substances sometimes obscure the relevant peaks. The aim of this study was to develop a sensitive and specific LC-MS/MS method for plasma free metanephrines.
Methods: After solid-phase extraction, chromatographic separation of normetanephrine (NMN) and metanephrine (MN) was accomplished by use of a cyano analytical column. NMN, MN, d3-NMN, and d3-MN positive ions were detected in the multiple-reaction monitoring mode using the specific transitions m/z 166
134, 180
148, 169
137, and 183
151, respectively, with an atmospheric pressure chemical ionization source.
Results: Multiple calibration curves exhibited consistent linearity and reproducibility. Interassay imprecision values (CV; n = 20) for NMN at 0.64, 1.9, and 2.7 nmol/L were 6.6%, 7.8%, and 13%, respectively. Interassay CV for MN at 0.60, 1.2, and 2.1 nmol/L (n = 20) were 9.2%, 6.8%, and 9.8%, respectively. The mean recoveries of NMN and MN relative to the internal standard were 100% and 96%, respectively. The assays were linear between 0.20 and 10.0 nmol/L. Deming regression of HPLC and LC-MS/MS results yielded slopes of 0.93 (95% confidence interval, 0.890.98) and 0.89 (0.850.93) and y-intercepts of -0.16 and 0.03 nmol/L for NMN (n = 132) and MN (n = 92), respectively.
Conclusions: This novel LC-MS/MS approach provides a precise, rapid, and specific alternative method to HPLC for the quantification of the low nanomolar concentrations of free metanephrines in plasma.
The following articles in journals at HighWire Press have cited this article:
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A. Algeciras-Schimnich, C. M. Preissner, W. F. Young Jr., R. J. Singh, and S. K. G. Grebe Plasma Chromogranin A or Urine Fractionated Metanephrines Follow-Up Testing Improves the Diagnostic Accuracy of Plasma Fractionated Metanephrines for Pheochromocytoma J. Clin. Endocrinol. Metab., January 1, 2008; 93(1): 91 - 95. [Abstract] [Full Text] [PDF] |
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T. M. Annesley Methanol-Associated Matrix Effects in Electrospray Ionization Tandem Mass Spectrometry Clin. Chem., October 1, 2007; 53(10): 1827 - 1834. [Abstract] [Full Text] [PDF] |
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R. J. Singh and G. Eisenhofer High-Throughput, Automated, and Accurate Biochemical Screening for Pheochromocytoma: Are We There Yet? Clin. Chem., September 1, 2007; 53(9): 1565 - 1567. [Full Text] [PDF] |
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W. H.A. de Jong, K. S. Graham, J. C. van der Molen, T. P. Links, M. R. Morris, H. A. Ross, E. G.E. de Vries, and I. P. Kema Plasma Free Metanephrine Measurement Using Automated Online Solid-Phase Extraction HPLC Tandem Mass Spectrometry Clin. Chem., September 1, 2007; 53(9): 1684 - 1693. [Abstract] [Full Text] [PDF] |
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M. d'Herbomez, G. Forzy, C. Bauters, C. Tierny, P. Pigny, B. Carnaille, F. Pattou, J.-L. Wemeau, and N. Rouaix An analysis of the biochemical diagnosis of 66 pheochromocytomas Eur. J. Endocrinol., May 1, 2007; 156(5): 569 - 575. [Abstract] [Full Text] [PDF] |
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R. L. Taylor, S. K. Grebe, and R. J. Singh Quantitative, Highly Sensitive Liquid Chromatography-Tandem Mass Spectrometry Method for Detection of Synthetic Corticosteroids Clin. Chem., December 1, 2004; 50(12): 2345 - 2352. [Abstract] [Full Text] [PDF] |
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