Automated GC-MS Determination of Δ9-Tetrahydrocannabinol, Cannabinol and Cannabidiol in Hair.
The determination of Δ(9)-tetrahydrocannabinol (THC), cannabinol (CBN) and cannabidiol (CBD) in hair is a major routine task in forensic laboratories worldwide. A comprehensively automated liquid-liquid extraction (LLE) method has been developed. The automation was carried out by an x-y-z sample robot equipped with modules capable of shaking, centrifugation and solvent evaporation. It comprises digestion of hair in sodium hydroxide solution, LLE, extract evaporation, reconstitution in silylation reagent, inlet derivatization and GC-MS analysis. Method validation guidelines of the Society for Toxicological and Forensic Chemistry were fulfilled. The limit of quantification (LOQ) was 0.01 ngmg for THC, 0.06 ngmg for CBN and 0.03 ngmg for CBD. This is below the required LOQ for THC (0.02 ngmg) in medical psychological assessments in Germany. Also it is far below the required LOQ of the Society of Hair Testing of 0.1 ngmg for THC. Four-round robin tests were passed successfully and several post- and ante-mortem samples were analyzed. To date the method is routinely employed at the Institute of Legal Medicine in Giessen, Germany. To the best of our knowledge, this is the first publication on a comprehensively automated classical LLE workflow in the field of hair analysis.