Thermal decomposition of CBD to Δ 9-THC during GC-MS analysis: A potential cause of Δ 9-THC misidentification

On the analysis of cannabidiol (CBD) e-liquid by gas chromatography-mass spectrometry, we experienced suspected thermal decomposition of CBD to Δ⁹-tetrahydrocannabinol (Δ⁹-THC). To clarify the factors involved in the decomposition, we evaluated the effects of the injection methods (splitless or split), injector temperatures (250, 225, 200, and 180 °C), and liner conditions (new liner or used liner) on the CBD decomposition. We also examined whether addition of methylamine to the dissolving solvent (methanol) inhibited the decomposition. Decomposition was not observed under split mode. However, under splitless mode, we observed that decomposition was promoted with the use of used liner and by high injector temperatures, and addition of methylamine to the dissolving solvent also suppressed the decomposition. Split injection was effective for preventing the decomposition; however, splitless injection enables detection of lower-concentrated Δ⁹-THC in CBD products than split injection. To balance sensitivity of Δ⁹-THC and inhibition of the thermal decomposition under splitless mode, we recommend using new liner for the analysis, addition of methylamine to the dissolving solvent, and maintenance of the injector temperature at 200 °C.