J Anal Toxicol. 2021 Jun 21:bkab068. doi: 10.1093/jat/bkab068. Online ahead of print.
The cannabinoids tetrahydrocannabinol (THC), tetrahydrocannabivarin (THCV), cannabidiol (CBD), cannabinol (CBN) and (-)-11-nor-9-carboxy-∆9-tetrahydrocannabinol (THC-COOH) were determined in 4773 hair samples. Confirmation of THC-COOH was by GC-MS/MS. Confirmation of THC, THCV, CBN and CBD was by LC-MS/MS on an AB Sciex QTRAP 6500+ LC-MS/MS. The purpose of this work was not to utilize any analyte other than THC-COOH as indicative of ingestion, but to assess the absence or presence, and relative concentrations, of the other cannabinoid analytes in hair of marijuana users vs. primarily cannabidiol users. In this regard, ten percent of samples contained significantly higher concentrations of CBD relative to THC than the other 90%. A concentration of CBD that is five times greater than that of THC was proposed as good evidence of primarily CBD ingestion.THC concentrations in the samples ranged from < LOD (5 pg/mg) to 47,808 pg/mg hair, varying widely in the relationship between parent THC and the metabolite THC-COOH. CBN was present in most samples, but concentrations relative to THC decreased with increasing THC concentrations. Only 26% of the samples contained THCV detectable by the method. When present, THCV concentrations averaged 1.77% of THC. A limitation of the study is the lack of subject histories to determine types and amounts of products used and mode of ingestion. Also, not all THC from external contamination may have been removed. Nonetheless, the data provide a useful guide as to what cannabinoids may be found in hair, at what concentrations, under conditions of marijuana vs. likely primarily CBD use.