Determination of cannabinoid vapor pressures to aid in vapor phase detection of intoxication

Abstract

The quest for a reliable means to detect cannabis intoxication with a breathalyzer is ongoing. To design such a device, it is important to understand the fundamental thermodynamics of the compounds of interest. The vapor pressures of two important cannabinoids, cannabidiol (CBD) and Δ9-tetrahydrocannabinol (Δ9-THC), are presented, as well as the predicted normal boiling temperature (NBT) and the predicted critical constants (these predictions are dependent on the vapor pressure data). The critical constants are typically necessary to develop an equation of state (EOS). EOS-based models can provide estimations of thermophysical properties for compounds to aid in designing processes and devices. An ultra-sensitive, quantitative, trace dynamic headspace analysis sampling called porous layered open tubular-cryoadsorption (PLOT-cryo) was used to measure vapor pressures of these compounds. PLOT-cryo affords short experiment durations compared to more traditional techniques for vapor pressure determination (minutes versus days). Additionally, PLOT-cryo has the inherent ability to stabilize labile solutes because collection is done at reduced temperature. The measured vapor pressures are approximately 2 orders of magnitude lower than those measured for n-eicosane, which has a similar molecular mass. Thus, the difference in polarity of these molecules must be impacting the vapor pressure dramatically. The vapor pressure measurements are presented in the form of Clausius-Clapeyron (or van’t Hoff) equation plots. The predicted vapor pressures that would be expected at near ambient conditions (25 °C) are also presented.

Particle size distribution and chemical composition of aerosolized vitamin E acetate

“…One of the distinct properties of both VEA and THC is a low vapor pressure (Lovestead and Bruno 2017; PubChem 2020) that may result in generation of aerosol particles of a small size in the low-submicron (<200 nm) or nano-size (<100 nm) range. Compounds with a low vapor pressure when heated to a high temperature can create critical supersaturation, leading to nucleation (Oxtoby 1992) while at the same time, because of lack of the surrounding molecules that support particle condensational growth (Bunz and Koyro 2000), aerosol size is reduced.…”

Toxicant Formation in Dabbing: The Terpene Story

“…The boiling point of THC has recently been predicted to be ca. 417 °C, 26 but vaporization can occur at temperatures lower than this by the use of a “carb cap” that reduces pressure on its surface during inhalation. 27…”

The influence of terpenes on the release of volatile organic compounds and active ingredients to cannabis vaping aerosols

“…56 )) compared to THC (417 °C (ref. 10 )) may translate to a reduced boiling point of the mixture, depressing the aerosolization temperature. β-Myrcene's enthalpy of vaporization may further depress reaction temperature.…”

“…THC transfer per puff (THC T ) was determined for CEC vaping experiments only. Aerosol PM analysis is sufficient for assessing THC T , as its low vapor pressure (2.6 × 10 −5 Pa) 10 affords it a high theoretically-calculated gas/particle partitioning constant ( K p = 0.31, calculated using Pankow [2001] 43 ), with 100.00% partitioned to the aerosol PM. CFPs were extracted in 1 : 1 methanol : acetonitrile, added with an internal standard (olivetol), and analyzed for THC content by HPLC-UV on a six-point internal standard calibration curve.…”

“…The cartridge contains 0.3–1.0 g cannabis oil, a viscous substance that may contain up to 90% of the psychoactive Δ 9 -tetrahydrocannabinol (THC, mp = rt, 9 bp = 416 °C (ref. 10 )). 5 Dabbing and CEC use have quickly surged in popularity, and one recent study showed 19.5% of past-month cannabis users reported CEC vaping, and 14.6% reported dabbing.…”