Comparative GC-MS and LC-MS/MS characterization of four 8-hydroxyhexahydrocannabinol stereoisomers and their TMS derivatives

PURPOSE: Hexahydrocannabinol (HHC) is an emerging semi-synthetic cannabinoid, but analytical data for all structurally confirmed stereoisomers of its hydroxylated metabolites remain limited. In this study, we synthesized all four stereoisomers of 8-hydroxyhexahydrocannabinol (8-OH-HHC) and comparatively characterized them, together with their trimethylsilyl (TMS) derivatives, by gas chromatography mass spectrometry (GC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). A particular analytical advantage of the present work is that it includes LC-MS/MS data for (8S,9R)-8-OH-HHC, for which no standard-based analytical data was previously available. METHODS: Four synthetic 8-OH-HHC stereoisomers were analyzed by GC-MS and LC-MS/MS. For GC-MS, both underivatized compounds and their TMS derivatives were examined. Retention behavior, electron ionization mass spectra, and LC-MS/MS transitions were compared among the stereoisomers. RESULTS: Under the tested GC conditions, the four stereoisomers and their TMS derivatives showed different retention times, although some differences were small and should be interpreted cautiously. Two pairs of stereoisomers exhibited similar electron ionization fragmentation patterns, whereas one pair showed differences in the relative abundances of selected ions. In addition to providing GC-MS data for all four underivatized stereoisomers, this study also provides GC retention and EI mass spectral data for all four TMS derivatives and a comparative evaluation of relative ion abundances among these closely related isomers. In LC-MS/MS, the stereoisomers showed partially overlapping transition patterns and closely eluting peaks under the tested conditions. CONCLUSIONS: These data provide a comparative analytical reference dataset for four structurally confirmed 8-OH-HHC stereoisomers and their TMS derivatives and may support future forensic studies of HHC-related compounds.