Development and Validation of a Liquid Chromatography High-Resolution Mass Spectrometry (LC-HRMS) Bioanalytical Method for Quantifying Cannabinoids in Whole Blood: Application for Determining Recent Cannabis Use.

Abstract

Cannabis legalization is expanding rapidly throughout the United States, but there is no reliable means of establishing recent use. To develop and validate a bioanalytical method for determination of Δ9-tetrahydrocannabinol (Δ9-THC), cannabinol, 11-hydroxy-Δ9-THC, 11-nor-9-carboxy-Δ9-THC, and 8β,11-dihydroxy-Δ9-THC in whole blood microsamples by liquid chromatography high-resolution mass spectrometry (LC-HRMS). Cannabinoid extraction from whole blood was performed using a mixture of n-hexane/ethyl acetate (90:10, v/v). Chromatographic separation was performed with a C18 column using a binary mobile phase gradient of water and acetonitrile, each with 0.1% formic acid. Detection was performed by positive ion mode heated electrospray ionization with full scan MS on an Orbitrap mass spectrometer. A clinical study was performed in 30 subjects to identify recent cannabis use based on analysis of cannabinoids in blood samples up to 200 min post-smoking. Acceptable linearity of all calibration curves was observed (r2>0.99) for all analytes over a 1-100 ng/mL concentration range, with acceptable accuracy. Limit of detection (LOD) was 0.5 ng/mL. Accuracy and precision met acceptance criteria for all analytes. Repeatability (CV) was <5% at low (3 ng/mL) and high (90 ng/mL) concentrations. In the clinical study, the ratios between 11-nor-9-carboxy-Δ9-THC and Δ9-THC fell immediately after smoking and returned to near baseline levels by 200 min post-smoking, which is consistent with recent use. The developed LC-HRMS bioanalytical method is suitable for quantification of five key cannabinoids in whole capillary blood microsamples and can be used in conjunction with a test for determining recent cannabis use.