LC/MS and GC/MS analysis of Δ⁹-tetrahydrocannabinol, Δ⁸-tetrahydrocannabinol and their metabolites

Abstract

 In blood testing for driving under the influence of cannabis, some foreign country authorities require detection of not only Δ⁹-tetrahydrocannabinol (Δ⁹-THC) but also its metabolites. Considering circulation of mixtures of Δ⁹-THC and Δ⁸-tetrahydrocannabinol (Δ⁸-THC), it is necessary to prepare the analytical method to achieve sufficient chromatographic separation of unchanged forms and the major metabolites of Δ⁹-THC and Δ⁸-THC and their differentiation by mass spectrometry. In this study, we examined simultaneous analytical conditions for Δ⁹-THC, Δ⁸-THC and their major metabolites by liquid chromatography/mass spectrometry (LC/MS) and gas chromatography/mass spectrometry (GC/MS). As major metabolites of Δ⁹-THC and Δ⁸-THC, we analyzed 11-hydroxy-forms (11-hydroxy-Δ⁹-THC for Δ⁹-THC and 11-hydroxy-Δ⁸-THC for Δ⁸-THC) and 11-nor-9-carboxy-forms (11-nor-9-carboxy-Δ⁹-THC for Δ⁹-THC and 11-nor-9-carboxy-Δ⁸-THC for Δ⁸-THC). In the LC/MS chromatograms, all compounds were completely separated by the cholesteryl column. In the mass spectrum, under positive condition, clear difference was recognized in MS² spectrum of 11-hydroxy-forms and MS² and MS³ spectra of 11-nor-9-carboxy-forms and it was possible to distinguish the compounds. However, Δ⁹-THC and Δ⁸-THC were difficult to be distinguished. In the GC/MS chromatograms, trimethylsilyl derivatives of Δ⁹-THC, Δ⁸-THC and their major metabolites were completely separated. And it is possible to distinguish the compounds by their mass spectra.