11-Nor-9-Carboxy-Δ8-Tetrahydrocannabinol, 7-Carboxy Cannabidiol, and 11-Nor-9-Carboxy-Δ9-Tetrahydrocannabinol in Urine by LC-MS/MS.

Δ8-Tetrahydrocannabinol (Δ8-THC) and cannabidiol (CBD) are increasingly popular cannabinoids. Measuring metabolites in urine is an important tool for detecting use and/or exposure as well as for monitoring elimination of these two drugs. Distinguishing between the metabolite 11-nor-9-carboxy-Δ8-tetrahydrocannabinol (Δ8-THC-COOH) and the analogous metabolite of the more common and naturally abundant Δ9-THC: 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (Δ9-THC-COOH) is analytically challenging due to structural similarities between the two compounds. Here, we present a method for separating the positional isomers Δ8-THC-COOH and Δ9-THC-COOH as well as 7-carboxy cannabidiol (CBD-COOH) in urine that includes reverse-phase solid-phase extraction (SPE), followed by liquid chromatographic separation with a perfluorophenyl column, and detection by tandem mass spectrometry (LC-MS/MS).