Rapid identification of marijuana using copper-phosphine ion complexation and commercialized paper spray...

Regulatory changes enacted through the 2018 Agriculture Improvement Act established the distinction between legal hemp and illicit marijuana based on a 0.3% Δ⁹-tetrahydrocannabinol (Δ⁹-THC) dry-weight threshold, reshaping analytical requirements for forensic laboratories. The influx of cannabis submissions and the quantitative requirements for marijuana identification have contributed to controlled substance backlogs and operational strain, prompting the adoption of more conservative semi-quantitative 1% decision-point methodologies. Differentiating hemp and marijuana is further complicated by the isomeric nature of Δ⁹-THC and cannabidiol (CBD), often requiring time-intensive chromatographic methods, including gas chromatography and liquid chromatography. This study provides a rapid, direct mass spectrometry approach for marijuana identification using copper-phosphine ion complexation and commercialized paper spray ionization-mass spectrometry (PSI-MS). Thirteen cannabinoids and a deuterated internal standard, Δ⁹-THC-d₉, were characterized in the presence of [Cu(PPh₃)₂(ACN)₂]BF₄, generating characteristic copper-bound, oxidized cannabinoid species. A [Cu+2PPh₃+Δ⁹-THC+O-2H]⁺ complex was observed at m/z 915, whereas CBD did not form an observable complex, thereby eliminating CBD interference for Δ⁹-THC quantitation. A semi-quantitative 1% decision-point assay was established by fortifying cannabis samples with Δ⁹-THC-d₉ at a 1% administrative threshold and determining whether the post-decarboxylation Δ⁹-THC content exceeds the 1% administrative threshold. Validation studies established selectivity, accuracy, precision, expanded uncertainty, carryover, and limit of detection. The validated method was applied to methanolic extracts of 36 decarboxylated authentic cannabis samples, resulting in a 94% corrected identification rate, with two misidentifications due to high cannabinol (CBN) concentrations. The developed method enables marijuana identification in approximately 4 minutes, enhancing laboratory throughput and potentially minimizing casework backlogs.