UHPLC-MS-MS Determination of THC, CBD and Their Metabolites in Whole Blood of Light Cannabis Smokers

"Light cannabis" is a product legally sold in Europe with Delta(9)-tetrahydrocannabinol (THC) concentration <0.2% and variable cannabidiol (CBD) content. In this study, we aimed to assess the time courses of THC and metabolites (11-nor-9-carboxy-THC and 11-hydroxy-THC) and CBD and metabolites (CBD-7-oic acid, 7-hydroxy-CBD, 6 alpha-hydroxy-CBD and 6 beta-hydroxy-CBD) in whole blood of 10 healthy participants after smoking one or four light cannabis cigarettes (0.16% THC and 5.8% CBD). Blood samples were collected 0.5-4 h after administration. Blood analysis was performed by reversed-phase ultra-performance liquid chromatography-tandem mass spectrometry in multiple reaction monitoring mode after glucuronide hydrolysis and liquid-liquid extraction in basic and acidic conditions. The method was validated following the most recent guidelines in toxicology: the method was linear, accurate, precise and sensitive (lower limits of quantification ranged from 0.005 to 0.01 ng/mL); carryover, matrix effect, recovery, process efficiency and dilution integrity were also assessed. As previously reported, the main metabolites of THC were THC-COOH and then 11-OH-THC, and the main metabolites of CBD were 7-OH-CBD and then 7-COOH-CBD. The time of the first collection, which likely occurred after the maximal concentration of most of the analytes, and the short monitoring time, up to 4 h after smoking, limited the evaluation of the pharmacokinetic parameters.