Micro extraction by packed sorbent coupled to liquid chromatography tandem mass spectrometry for the rapid and sensitive determination of cannabinoids in oral fluids

The evaluation of oral fluids (OFs) levels is useful in proving drug consumption, particularly for monitoring abuse in workplaces and for the driving under the influence of drugs (DUIDs) programs. OF is a complex matrix and a small amount of sample is available, especially after cannabis smoking. This paper reports a method for the determination of cannabinoids and metabolites in OF: THC, 11-hydroxy-THC (OH-THC) and THC-COOH. Cannabidiol (CBD) and cannabinol (CBN) were also detected by LC–MS/MS. The OF pre-treatment was based on micro-extraction by packed sorbent (MEPS), a recently developed solid phase extraction technique which operates with small sample volumes: only 125 μL of sample was required, allowing the collection by simple expectoration. Analytes elution was achieved using 2 × 25 μL of 50 mM NH4OH in methanol. A rapid and effective clean-up has been obtained with satisfactory recovery values and a negligible matrix effect. The LOQs ranged between 0.020 ng mL−1 for THC-COOH and 0.40 ng mL−1 for OH-THC. The chromatographic conditions obtained with a fused-core column allowed a good separation of the analytes in 6 min only. The whole procedure has been validated according to SOFT/AAFS guidelines.