Evaluation of a Delta-9-Tetrahydrocannabinol Carboxylic Acid (Δ9-THC-COOH) Immunoassay and a Gas Chromatography-Mass Spectrometry (GC-MS) Method for the Detection of Delta-8-Tetrahydrocannabinol Carboxylic Acid (Δ8-THC-COOH)

Background: Delta-8 tetrahydrocannabinol (Delta 8-THC) is a naturally occurring or synthetically prepared cannabinoid that elicits psychological and physiological experiences commonly reported for its more infamous isomer, delta-9 tetrahydrocannabinol (Delta 9-THC). Unlike Delta 9-THC, Delta 8-THC products are generally legal under federal law and there has been a rise in their usage. One of the main targets for detection and quantitation of Delta 9-THC is its inactive metabolite, 11-nor-9-carboxy-Delta 9-tetrahydrocannabinol (Delta 9-THC-COOH). Methods: This study evaluated the ability of the currently used Delta 9-THC-COOH immunoassay and gas chromatography-mass spectrometry (GC-MS) methods to detect 11-nor-9-carboxy-Delta 8-tetrahydrocannabinol (Delta 8-THC-COOH) and distinguish it from Delta 9-THC-COOH. Results: The EMIT II Plus(R) Cannabinoid immunoassay for Delta 9-THC-COOH with a cutoff of 20 ng/mL showed positive results for Delta 8-THC-COOH with concentrations of 30 ng/mL or higher. Although many of the ion fragments generated by mass spectrometry were found to overlap between the 2 compounds, the GC-MS method presently used to quantify Delta 9-THC-COOH separated the 2 compounds sufficiently to identify them independently by relative retention time. Conclusion: Current immunoassays and GC-MS methods should be evaluated for the ability to detect and distinguish the presence of Delta 8-THC-COOH.