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Clinical Chemistry and Laboratory Medicine (CCLM)

Published in Association with the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM)

Editor-in-Chief: Plebani, Mario

Editorial Board Member: Gillery, Philippe / Kazmierczak, Steven / Lackner, Karl J. / Lippi, Giuseppe / Melichar, Bohuslav / Schlattmann, Peter / Whitfield, John B.

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Rank 5 out of 29 in category Medical Laboratory Technology in the 2013 Thomson Reuters Journal Citation Report/Science Edition



Pitfalls in measuring the endocannabinoid 2-arachidonoyl glycerol in biological samples

Michael Vogeser1 / Gustav Schelling1

1Institute of Clinical Chemistry, Hospital of the University of Munich, Munich, Germany

2Department of Anesthesiology, Hospital of the University of Munich, Munich, Germany

Corresponding author: Michael Vogeser, MD, Institute of Clinical Chemistry, Hospital of the University of Munich, Marchioninistraße 15, 81377 Munich, Germany Phone: +49-89-70953221, Fax: +49-89-70953240,

Citation Information: Clinical Chemical Laboratory Medicine. Volume 45, Issue 8, Pages 1023–1025, ISSN (Online) 14374331, ISSN (Print) 14346621, DOI: 10.1515/CCLM.2007.197, August 2007

Publication History

Published Online:


Background: The endocannabinoid 2-arachidonoyl glycerol (2-AG) undergoes spontaneous isomerization to biologically inactive 1-AG. This effect has not been adequately addressed in previous studies that reported 2-AG concentrations in biological samples.

Methods: Liquid chromatography tandem-mass spectrometry (LC-MS/MS) was used for 1-AG and 2-AG analyses.

Results: Identical collision-induced disintegration spectra were found for 1-AG and 2-AG. For specific detection of both compounds, which share a common mass transition, baseline chromatographic separation is mandatory, even when applying MS/MS technology with its generally high detection specificity. When using standard chromatographic conditions with the very short run times typically used in LC-MS/MS methods, co-elution of 2-AG with 1-AG, which is present in human serum, causes false 2-AG results.

Conclusions: Our data highlight that the analytical specificity of MS/MS can be limited by interference from isobaric isomers with identical disintegration patterns. The specificity of this technology must be carefully evaluated for each individual application.

Clin Chem Lab Med 2007;45:1023–5.

Keywords: 1-arachidonoyl glycerol (1-AG); 2-arachidonoyl glycerol (2-AG); endocannabinoids; interference; isomers; liquid chromatography tandem-mass spectrometry (LC-MS/MS)

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