Detection of ∆⁹-tetrahydrocannabinol in exhaled breath after cannabis smoking and comparison with oral fluid

Exhaled breath is commonly used in alcohol testing, but has been recently demonstrated by scientists from Sweden, Germany, Belgium, Switzerland, and the United States to contain a large number of both volatile and non-volatile substances that can be measured using dedicated devices. ExaBreath^® is a sampling device that collects the bio-aerosol particles from the donor. Approximately 2 min exhaled breath is enough for the test. The device collects the very small bio-aerosols on a filter, which is consecutively incubated into methanol to release drugs at a laboratory. Four occasional cannabis smokers were recruited for this study. Oral fluid, collected with the Quantisal^® device, and exhaled breath were simultaneously collected up to 6 h after smoking a standard joint of cannabis. ∆⁹-Tetrahydrocannabinol (THC) was tested using liquid chromatography–tandem mass spectrometry (MS/MS) or gas chromatography–MS/MS for exhaled breath and oral fluid, respectively. Linearity, precision and limit of quantification (5 pg/filter and 0.5 ng/mL for exhaled breath and oral fluid, respectively) were established. In each analytical batch, low and high controls were included. THC was identified in exhaled breath up to 6 h after smoking from all the four subjects, with concentrations in the range 15–1598 pg/filter. THC breath concentrations significantly decreased with time after smoking in all four participants. All the oral fluid specimens tested positive for THC over the 6 h of the study, with concentrations in the range 1–89 ng/mL. 11-Nor-9-carboxy-Δ⁹-tetrahydrocannabinol, the main metabolite of THC was also analysed, but was undetectable in both exhaled breath and oral fluid. This study gives further support to the possibility of using exhaled breath as a new matrix to document exposure to drugs, particularly for cannabis.