The transition of cannabinoids and terpenes in cannabis from "solid" to vapor or smoke in a joint (cannabis cigarette) was examined. It was published in the journal Cannabis and Cannabinoid Research in October 2023.
Three different cannabis flower chemovars were tested. Two were THC dominant with little CBD, and one was balanced with similar amounts of THC and CBD:
- 14.3% THC, <0.1% CBD
- 23.5% THC, <0.1% CBD
- 9% THC, 10.6% CBD
The authors created a smoking machine that "inhaled" 35ml in 5.6 seconds with the interval between puffs set to 15 seconds. The smoke was trapped in an ethanol solution and then tested via HPLC (cannabinoids) and gas chromatography (terpenes and terpenoids).
The bottom line is they found the concentration of cannabinoids and terpenes in the smoke increases as the joint is smoked. The first part of the joint will have a higher concentration of terpenes and lower concentration of cannabinoids than the last part of the joint. This is because almost all cannabis terpenes have lower boiling points than cannabinoids.
Overall, the amount of cannabinoids and terpenes in each inhalation increases as the joint is smoked. The second half of a joint could easily have TWICE the concentration of the first half:
for example, if one half of the cigarette is used in the morning and the other half for the night, the dose in the latter might approach twice that in the former.
terpenes are inhaled before the cannabinoids are. The same is true for using vaporizers.
"Roaches" are thus stronger, but usually don't taste as good due primarily to the previous vaporization of lower boiling point monoterpenes like myrcene, pinene, linalool, terpinolene, and limonene. The monoterpenes found in cannabis usually boil below 450F (233C), whereas the sesquiterpenes usually boil above those temperatures. Cannabinoids typically boil above 750F (400C).
Authors' results and conclusions:
Results demonstrated increased cannabinoid content in the cigarette sections closer to the mouth, as compared with those closer to the lit end.
cannabinoid content in the inhaled smoke increases as smoking progresses
Monoterpenes, having lower boiling points reach the smoke before the sesquiterpenes and cannabinoids do
The full text article is here at LiebertPub.com.
Eyal AM, Hen-Shoval D, Schlesinger D, Berneman-Zeitouni D, Raz N. Inconsistency in the Composition of the Smoke of a Cannabis Cigarette as Smoking Progresses: Results, Mechanism, and Implications. Cannabis Cannabinoid Res. 2023 Oct 17. doi: 10.1089/can.2023.0123. Epub ahead of print. PMID: 37847234.