Stability of Δ<sup>9</sup>- and Δ<sup>8</sup>-tetrahydrocannabinol acetate in e-liquid during storage period (Second report)

Abstract

We examined the stability of Δ9-tetrahydrocannabinol acetate (Δ9-THC-OAc) and Δ8-tetrahydrocannabinol acetate (Δ8-THC-OAc) in e-liquid products. Eight samples were heated at 30℃ for 28 days and one of them was heated at 70℃ for 2, 4, 8, 10, and 15 days. Residual ratios of Δ9-THC-OAc and Δ8-THC-OAc were evaluated by gas chromatography with flame ion detection and their degradation products were examined by gas chromatography/mass spectrometry (GC/MS). Some samples were tested for solubility in hexane and were submitted to GC/MS analysis to detect propylene glycol and glycerol. After a 28-day incubation at 30℃, Δ9-THC-OAc was slightly decomposed (residual ratio: 84.5–94.2%) but Δ8-THC-OAc was almost stable (residual ratio: 95.2–108.9%). Heating at 70℃ decomposed not only Δ9-THC-OAc but also Δ8-THC-OAc. The decomposition proceeded rapidly in the initial 2 days then slowly until 15 days later. The degradation products, four putative one-oxygen-atom adducts and cannabinol, were detected but deacetylated products (Δ9-tetrahydrocannabinol and Δ8-tetrahydrocannabinol) were not detected. All the samples tested were completely dissolved in hexane differently from propylene glycol and glycerol. Propylene glycol and glycerol were not detected from the samples completely dissolved in hexane. This study indicated that deacetylation of Δ9-THC-OAc and Δ8-THC-OAc did not proceed when the sample did not contain propylene glycol and glycerol.