Pressurized liquid extraction for the determination of cannabinoids and metabolites in hair: Detection of cut-off values by high performance liquid chromatography–high resolution tandem mass spectrometry

• Fast method for the determination of cannabinoids and metabolites in hair.
• Extraction from hair using pressurized liquid extraction with water modified with SDS.
• Detection of 11-nor-9-carboxy-THC in hair below cut-off value by HPLC–HRMS/MS.
• Validation following SWGTOX guidelines for confirmatory analysis.

Hair analysis has become a routine procedure in most forensic laboratories since this alternative matrix presents clear advantages over classical matrices; particularly wider time window, non-invasive sampling and good stability of the analytes over time. There are, however, some major challenges for the analysis of cannabinoids in hair, mainly related to the low concentrations of 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH), that is the major metabolite. In this study a fast, accurate and sensitive method for the determination of cannabinol, cannabidiol, THC and THC-COOH in hair has been developed. The extraction of analytes from hair (50 mg) is based on an automated pressurized liquid extraction (PLE) using water modified with the surfactant sodium dodecyl sulphate as eluent phase. PLE extract is then cleaned up by SPE using polymeric reversed phase cartridges Strata XL before the injection in the HPLC–HRMS/MS system. Chromatographic conditions obtained with a fused-core column allowed a good separation of the analytes in less than 4 min. The whole procedure has been validated according to SWGTOX guidelines. The LLOQs obtained for THC-COOH and the other analytes were respectively 0.1 and 2 pg/mg. To the best of our knowledge, this is the first LC–MS/MS based method that allows the detection of THC-COOH in hair at values lower than the cut-off.