Differentiation of Δ⁹-THC and CBD Using Silver-Ligand Ion Complexation and Electrospray Ionization Tandem Mass Spectrometry (ESI-MS/MS)

Abstract

The 2018 Farm Bill defines marijuana as Cannabis sativa L. or any derivative thereof that contains greater than 0.3% Δ 9 -tetrahydrocannabinol (Δ 9 -THC) on a dry weight basis. The main cannabinoids present in Cannabis sativa L., Δ 9 -THC and cannabidiol (CBD), are structural isomers that cannot be differentiated using direct mass spectrometry with soft ionization techniques alone. Due to the classification of marijuana as a Schedule I controlled substance, the differentiation of Δ 9 -THC and CBD is crucial within the seized drug community. This study explores the use of Ag-ligand ion complexation and electrospray ionization tandem mass spectrometry (ESI-MS/MS) for the differentiation of Δ 9 -THC and CBD using six different Ag complexes. Differences between the binding affinities of Δ 9 -THC and CBD for [Ag(PPh 3 )(OTf)] 2 lead to the formation of unique product ions at m/z 421/423, m/z 353/355, and m/z 231 for CBD, enabling the differentiation of CBD from Δ 9 -THC. When applied to the analysis of known Δ 9 -THC:CBD mixture ratios, the developed [Ag(PPh 3 )(OTf)] 2 ion complexation method was able to differentiate Δ 9 -THC-rich and CBD-rich samples based on the average abundance of the product ions at m/z 421/423. The developed approach was then applied to methanolic extracts of 20 authentic cannabis samples with known Δ 9 -THC and CBD compositions, resulting in a 95% correct classification rate. Even though the developed Ag-ligand ion complexation method was only demonstrated for the qualitative differentiation of Δ 9 -THC-rich and CBD-rich cannabis, this study establishes a foundation for the use of Ag-ligand ion complexation that is essential for future quantitative approaches.