Hair analysis for Δ⁹‐tetrahydrocannabinolic acid A (THCA‐A) and Δ⁹‐tetrahydrocannabinol (THC) after handling cannabis plant material

Abstract

A previous study has shown that Δ(9) -tetrahydrocannabinolic acid A (THCA-A), the non-psychoactive precursor of Δ(9) -tetrahydrocannabinol (THC) in the cannabis plant does not get incorporated in relevant amounts into the hair through the bloodstream after repeated oral intake. However, THCA-A can be measured in forensic hair samples in concentrations often exceeding the detected THC concentrations. To investigate whether the handling of cannabis plant material prior to consumption is a contributing factor for THC-positive hair results and also the source for THCA-A findings in hair, a study comprising ten participants was conducted. In this study, the participants rolled a marijuana joint on five consecutive days and hair samples of each participant were obtained. Urine samples were taken to exclude cannabis consumption prior to and during the study. THCA-A and THC could be detected in the hair samples from all participants taken at the end of the exposure period (concentration range: 15-1800 pg/mg for THCA-A and < 10-93 pg/mg for THC). Four weeks after the first exposure, THCA-A could still be detected in the hair samples of nine participants (concentration range: 4-57 pg/mg). Furthermore, THC could be detected in the hair samples of five participants (concentration range: < 10-17 pg/mg). Based on these results, it can be concluded that at least parts of the THC as well as the major part of THCA-A found in routine hair analysis derives from external contamination caused by direct transfer through contaminated fingers. This finding is of particular interest in interpreting THC-positive hair results of children or partners of cannabis users, where such a transfer can occur due to close body contact. Analytical findings may be wrongly interpreted as a proof of consumption or at least passive exposure to cannabis smoke. Such misinterpretation could lead to severe consequences for the people concerned.

Simultaneous quantification of 11 cannabinoids and metabolites in human urine by liquid chromatography tandem mass spectrometry using WAX-S tips

“…THCAA concentrations were monitored in plasma and whole blood [24], blood serum and urine [25] and oral fluid [26, 27]. THCAA also was demonstrated in hair after cannabis consumption, passive exposure and external contamination [28, 29]. The plant constituent THCV was recently administered in a controlled study investigating if THCV inhibits THC effects [30], as it was suggested that THCV is a receptor neutral antagonist [31].…”

Micro-pulverized extraction pretreatment for highly sensitive analysis of 11-nor-9-carboxy-Δ9-tetrahydrocannabinol in hair by liquid chromatography/tandem mass spectrometry

“…In forensic cases, hair samples are often used as evidence for drug use, as trace amounts of certain compounds can be detected in hair. THC and THCA‐A are not suitable markers for cannabis intake due to the potential for external contamination, such as in the adsorption of second‐hand smoke by hair . Therefore, a primary metabolite of THC, 11‐nor‐9‐carboxy‐THC (THC‐COOH), is typically used as a marker to confirm the intake of cannabis (Supplementary Fig.…”

“…THC and THCA-A are not suitable markers for cannabis intake due to the potential for external contamination, such as in the adsorption of second-hand smoke by hair . [1,2] Therefore, a primary metabolite of THC, 11-nor-9-carboxy-THC (THC-COOH), is typically used as a marker to confirm the intake of cannabis ( Supplementary Fig. S1, see Supporting Information).…”

Simultaneous quantification of THC‐COOH, OH‐THC, and further cannabinoids in human hair by gas chromatography–tandem mass spectrometry with electron ionization applying automated sample preparation

“…External hair contamination of THCA‐A has been reported, caused primarily by handling Cannabis sativa plant material and side stream smoke . Diffusion and incorporation of the cannabinoid into the hair matrix can therefore occur, which cannot be completely removed, even by extensive washing/decontamination steps.…”