Detection of Δ9-tetrahydrocannabinolic acid A in human urine and blood serum by LC-MS/MS

9-Tetrahydrocannabinolic acid A (Delta 9-THCA-A) is the precursor of Delta 9-tetrzthydrocannabinol (Delta 9-THC) in hemp plants. During smoking, the non-psychoactive Delta 9-THCA-A is converted to Delta 9-THC, the main psychoactive component of marihuana and hashish. Although the decarboxylation of Delta 9-THCA-A to Delta 9-THC was assumed to be complete - which means that no Delta 9-THCA-A should be detectable in urine and blood serum of cannabis consumers - we found Delta 9-THCA-A in the urine and blood serum samples collected from police controls of drivers suspected for driving under the influence of drugs (DUID). For LC-MS/MS analysis, urine and blood serum samples were prepared by solid-phase extraction. Analysis was performed with a phenylhexyl column using gradient elution with acetonitrile. For detection of Delta 9-THCA-A, the mass spectrometer (MS) (SCIEX API 365 triple-quadrupole MS with TurbolonSpray source) was operated in the multiple reaction monitoring (MRM) mode using the following transitions: m/z 357 -> 313, m/z 357 -> 245 and m/z 357 -> 191. Delta 9-THCA-A could be detected in the urine and blood serum samples of several cannabis consumers in concentrations of up to 10.8 ng/ml in urine and 14.8 ng/ml in serum. The concentration of Delta 9-THCA-A was below the Delta 9-THC concentration in most serum samples, resulting in molar ratios of Delta 9-THCA-A/Delta 9-THC of approximately 5.0-18.6%. Only in one case, where a short elapsed time between the last intake and blood sampling is assumed, the molar ratio was 18.6% in the serum. This indicates differences in elimination kinetics, which need to be investigated in detail. Copyright (c) 2007 John Wiley & Sons, Ltd.