Journal Article

Detection of THCA in Oral Fluid by GC-MS-MS

David Day, David J. Kuntz, Michael Feldman and Lance Presley

in Journal of Analytical Toxicology

Volume 30, issue 9, pages 645-650
Published in print November 2006 | ISSN: 0146-4760
Published online November 2006 | e-ISSN: 1945-2403 | DOI:
Detection of THCA in Oral Fluid by GC-MS-MS

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  • Medical Toxicology
  • Toxicology (Non-medical)


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A major marijuana metabolite, 11-nor-9-carboxy-tetrahydrocannabinol (THCA), has been identified in oral fluids from donors that previously tested positive for Δ9-tetrahydrocannabinol (THC). The method consisted of solid-phase extraction of the oral fluid samples followed by gas chromatography-tandem mass spectrometry analysis of the extracts. Testing for THCA was performed on 223 oral fluid samples previously analyzed for THC. The THCA assay was linear from 10 to 240 pg/mL. The mean recovery of spiked THCA in oral fluid was 104%, and precision was 4% at 20 pg/mL using fortified negative samples. This method was rugged and robust, providing detection and quantification of THCA in oral fluids at levels not previously reported. Results of this study showed that THCA was detectable in 21 of 26 oral fluid samples previously reported positive for THC. The range of concentrations from these samples was from 10 pg/mL up to 142 pg/mL THCA.

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Subjects: Medical Toxicology ; Toxicology (Non-medical)

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