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

Couch A.; Zall C.; Davidson J. · Analytical methods : advancing methods and applications · 2026

**Background & Methods** This analytical methods study developed and validated a rapid mass spectrometry approach for distinguishing legal hemp from illicit marijuana based on the 0.3% Δ9-tetrahydrocannabinol (Δ9-THC) regulatory threshold established by the 2018 Agriculture Improvement Act. The methodology employed copper-phosphine ion complexation with commercialized paper spray ionization-mass spectrometry (PSI-MS) to characterize 13 cannabinoids in 36 decarboxylated authentic cannabis samples, with validation studies assessing selectivity, accuracy, precision, expanded uncertainty, carryover, and limit of detection. **Key Findings** - The copper-phosphine complex [Cu(PPh3)2(ACN)2]BF4 selectively formed a characteristic complex with Δ9-THC ([Cu+2PPh3+Δ9-THC+O-2H]+ at m/z 915) while not forming observable complexes with cannabidiol (CBD), eliminating CBD interference and enabling accurate Δ9-THC quantitation. - A semi-quantitative 1% decision-point assay was successfully established using Δ9-THC-d9 as an internal standard, with validation demonstrating the method's ability to determine whether post-decarboxylation Δ9-THC content exceeds administrative thresholds. - Application to 36 cannabis samples achieved a 94% corrected identification rate, with two misidentifications attributable to high cannabinol (CBN) concentrations, completing analysis in approximately 4 minutes per sample. **Dosage & Administration** Not reported. **Safety & Adverse Effects** Not reported. **Evidence Quality** This is a methodological validation study rather than a clinical trial, representing a lower level of evidence (analytical method development). Key limitations include the modest sample size (n=36), lack of blinded analysis, and potential interference from high CBN concentrations affecting accuracy. The 94% identification rate, while encouraging, indicates room for improvement in handling samples with elevated CBN levels. The study's strength lies in comprehensive analytical validation and practical applicability to forensic laboratory workflows. The rapid 4-minute turnaround time represents a significant operational advantage for addressing controlled substance backlogs, though clinical or epidemiological applications were not assessed.

More recent cannabis research