New perspectives on THCA decarboxylation and accurate GC-MS quantitation of Total THC in Cannabis using analyte...

Forensic and commercial laboratories rely on well-characterized analytical methods to accurately determine total tetrahydrocannabinol (total THC), which is the sum of decarboxylated tetrahydrocannabinolic acid (THCA) and delta-9-tetrahydrocannabinol (Δ⁹-THC) in Cannabis sativa samples. The Agriculture Improvement Act of 2018 restricts the level of total THC allowed in Cannabis for classification as hemp for commercial purposes. Gas chromatography with mass spectrometry detection (GC-MS) is frequently employed for Cannabis measurements due to its simplicity and speed of analysis. However, several issues complicate the determination of total THC by GC-MS, which are well-documented but unresolved. In the current study, the origins of potential GC-MS method biases are investigated, and novel approaches are presented to mitigate interferences. The behavior of THCA and Δ⁹-THC during GC-MS analyses was studied extensively using test solutions containing their isotopically labeled analogs. A plant matrix effect was identified that significantly increased THCA and Δ⁹-THC responses for Cannabis extracts compared with calibrant solutions. A mechanism is proposed based on the interaction of THCA and Δ⁹-THC with silanols present on heated inlet surfaces. The use of active site blocking agents, known as analyte protectants, reduced these interactions and achieved suitable conditions for quantitation of total THC by GC-MS. When Cannabis plant extracts and calibrants were processed under the recommended conditions, the results were comparable to liquid chromatography with photodiode array (LC-PDA) analysis. The experimental findings ultimately provide evidence to explain the behavior of cannabinoids in the GC-MS system and offer new options for improving the accuracy of total THC measurements.