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Clinical Chemistry 48: 332-337, 2002;
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(Clinical Chemistry. 2002;48:332-337.)
© 2002 American Association for Clinical Chemistry, Inc.

Rapid Analysis of Metanephrine and Normetanephrine in Urine by Gas Chromatography-Mass Spectrometry

David K. Crockett1a, Elizabeth L. Frank2 and William L. Roberts2

1 ARUP Laboratories, Inc., 500 Chipeta Way, Salt Lake City, UT 84108.

2 Department of Pathology, University of Utah School of Medicine, Salt Lake City, UT 84132.

aAuthor for correspondence. E-mail crockedk{at}aruplab.com.

Background: Widely used HPLC methods for quantification of metanephrine and normetanephrine in urine often have long analysis times and are frequently plagued by drug interferences. We describe a gas chromatography-mass spectrometry method designed to overcome these limitations.

Methods: Metanephrine and normetanephrine conjugates were converted to unconjugated metanephrine and normetanephrine by acid hydrolysis. To avoid the rapid decomposition of the deuterated internal standards (metanephrine-d3 and normetanephrine-d3) under hydrolysis conditions, the internal standards were added after hydrolysis. Solid-phase extraction was used to isolate the hydrolyzed metanephrines from urine. Samples were concentrated by evaporation, then derivatized simultaneously with N-methyl-N-(trimethylsilyl)trifluoroacetamide and N-methyl-bis-heptafluoro-butryamide at room temperature.

Results: The assay was linear from 25 to 7000 µg/L. The intraassay CVs were <5% and the interassay CVs <12%. Comparison with a routine HPLC method (n = 192) by Deming regression yielded a slope of 1.00 ± 0.02 µg/L, an intercept of -5.8 ± 7.8 µg/L, and Sy|x = 50.6 µg/L for metanephrine and a slope of 0.94 ± 0.03, intercept of 19 ± 11 µg/L, and Sy|x = 60 µg/L for normetanephrine. The correlation coefficients (r) were calculated after log transformation of the data and gave r = 0.97 for metanephrine and r = 0.97 for normetanephrine. Interference from common medications or drug metabolites was seen in <1% of samples. The time between sequential injections was <7 min.

Conclusions: This new gas chromatography-mass spectrometry assay for total fractionated metanephrines is rapid, compares well with a standard HPLC assay, and avoids most drug interferences that commonly affect HPLC assays for urine metanephrines.




The following articles in journals at HighWire Press have cited this article:


Home page
 Clin. Chem.Home page
R. J. Singh, S. K. Grebe, B. Yue, A. L. Rockwood, J. C. Cramer, Z. Gombos, G. Eisenhofer, and S. Binder
Precisely Wrong? Urinary Fractionated Metanephrines and Peer-Based Laboratory Proficiency Testing * A representative for Bio-Rad responds:
Clin. Chem., February 1, 2005; 51(2): 472 - 474.
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