Differentiating Δ⁸-THC and Δ⁹-THC Isomers: Mass Spectrometry Analysis and Computational Explanation

Area of Science:

• Forensic Chemistry
• Analytical Chemistry
• Organic Chemistry

Background:

• Isomerism is a common challenge in identifying new psychoactive substances (NPSs).
• Delta-8-tetrahydrocannabinol (Δ⁸-THC) is a double-bond isomer of delta-9-tetrahydrocannabinol (Δ⁹-THC), often synthesized from cannabidiol (CBD).
• Accurate identification of NPS isomers is crucial for forensic laboratories due to structural similarities.

Purpose of the Study:

• To investigate and differentiate the mass spectrometry (MS) fragmentation patterns of Δ⁸-THC and Δ⁹-THC.
• To establish reliable methods for distinguishing between these two isomers in forensic analysis.

Main Methods:

• Systematic investigation using gas chromatography-quadrupole time-of-flight mass spectrometry (GC-Q-TOF/MS).
• Analysis using liquid chromatography coupled to high-resolution quadrupole Orbitrap mass spectrometry (LC-Q-Orbitrap/MS).
• Computational studies to elucidate fragmentation mechanisms.

Main Results:

• GC-Q-TOF/MS revealed significant differences in ion abundance (m/z 314 and 299) between Δ⁸-THC and Δ⁹-THC due to radical stability.
• The ratio of ion abundance at m/z 314 and 299 effectively distinguishes between the isomers.
• LC-Q-Orbitrap/MS showed similar fragmentation, but computational analysis identified distinct mechanisms (retro Diels-Alder vs. double-hydrogen transfer) leading to different EI-MS peaks (m/z 246 for Δ⁸-THC, m/z 231 for Δ⁹-THC).

Conclusions:

• Accurate differentiation between Δ⁸-THC and Δ⁹-THC is achievable through MS analysis.
• This capability enhances drug laboratories' ability to analyze drug origins.
• Provides critical intelligence and scientific support for law enforcement agencies.