Emergence of Delta-8 Tetrahydrocannabinol (THC) in DUID Investigation Casework: Method Development, Validation and Application.

Cannabinoids is the most frequently reported illicit drug class in Driving Under the Influence of Drugs (DUID) investigation casework. In recent years, our laboratory observed an increasing rate of overlapping peaks for the cannabinoids confirmation performed using two-dimensional (2D)-High Performance Liquid Chromatography/Tandem Mass Spectrometry (LC-MS/MS). Starting in early 2018, the incidence of unresolved interfering substances increased, contributing to a higher rate of canceled testing that peaked at 3.7% in February 2019. The observed interference demonstrates a distinctive pattern affecting identifications and quantification of both Delta-9 THC and Delta-9 carboxy THC. An improved quantitative method was developed and validated to separate Delta-8 and -9 isomers and their metabolites in blood. All acceptance criteria were met with identical measurement ranges from the original method (lower limit of quantitation: 0.5 ng/mL for Delta-9 THC, 1.0 ng/mL for 11-Hydroxy Delta-9 THC, and 5.0 ng/mL for Delta-9 carboxy THC). Cannabinoids were extracted from whole blood using liquid-liquid extraction, separated in a 2D liquid chromatography system over a run-time of 10 min and detected by a tandem mass spectrometry system equipped with ESI source operating in positive ionization mode with scheduled multiple reaction mass spectrometric monitoring (MRM). The LC system consisted of a pair of Phenomenex® SecurityGuard™ C6 Phenyl (4x2 mm) cartridges for extracting the compounds with 5 mM ammonium formate buffer in deionized (DI) water and 0.1% formic acid in methanol as mobile phase, and a Phenomenex® Kinetex C18 column (100x3 mm) with 0.1% formic acid in DI water and 0.1% formic acid in methanol for LC separation at 45°C. Each set of isomers was fully resolved by the longer run-time method. To the authors' knowledge, this is the first report of a method that successfully quantitates these primary cannabinoids in blood specimens where significant concentrations of both Delta-9 and Delta-8 isomers are present.