Analysis of seven selected cannabinoids in human plasma highlighting matrix and solution stability assessments

Cannabis consumption has and continues to increase dramatically, as does its legalization for recreational and/or medicinal use at the state, but not at the federal level. The increased consumption and legalization have spurred significant cannabis focused research, with particular interest in defining the pharmacokinetic characteristics of this complex natural product. Supporting this research requires a bioanalytical method that accurately and simultaneously quantifies the primary cannabinoids and their metabolites. The objective of this method validation was to meet pre-specified sensitivity targets (0.5 ng/mL for most analytes) from a low sample volume (0.2 mL) and single extraction approach that could quantify Δ9-tetrahydrocannabinol, cannabidiol, and their metabolites. Moreover, we sought to rigorously characterize the stability of included cannabinoid analytes, both in solution and plasma. The developed assay required optimization of extraction and mobile phase solvents, as well as mass transitions to achieve the selectivity required to meet the desired sensitivity targets. Stability experiments indicated solution stability of no more than 6 months when stored in polypropylene at -30 or -80 °C and ∼3 years (34.5 months) of plasma stability when stored in polypropylene at -80 °C. The assay was successfully applied to ∼1650 samples without a batch failure. This validated LC-MS/MS assay provides unique information on cannabinoid stability and has been utilized to generate novel data on the pharmacokinetics of cannabis constituents and their metabolites.