Determination of cannabinoids in 50 μL whole blood samples by online extraction using turbulent flow chromatography and LC‐HRAM‐Orbitrap‐MS: Application on driving under the influence of drugs cases

Abstract

The analysis of cannabinoids in whole blood is usually done by traditional mass spectrometry (MS) techniques, after offline cleanup or derivatization steps which can be lengthy, laborious, and expensive. We present a simple, fast, highly specific, and sensitive method for the determination of Δ9‐tetrahydrocannabinol (THC), cannabidiol (CBD), cannabinol (CBN), 11‐hydroxy‐Δ9‐tetrahydrocannabinol (11‐OH‐THC), and 11‐nor‐9‐carboxy‐Δ9‐tetrahydrocannabinol (THC‐COOH) in 50 μL whole blood samples. After the addition of deuterated internal standards (IS) and a simple protein precipitation step, an online extraction of sample supernatants using turbulent flow chromatography (TurboFlow—Thermo Scientific) was carried out. Analytes were separated on a C18 analytical column and detected by LC‐HRAM‐Orbitrap‐MS using a Thermo Scientific Q Exactive Focus MS system. MS detection was performed in polarity switching and selected ion monitoring (SIM) modes using five specific acquisition windows, at a resolution of 70,000 (FWHM). Total run time was about 10 min including preanalytical steps. Method validation was carried out by determining limit of detection (LOD), lower limit of quantitation (LLOQ), linearity range, analytical accuracy, intra‐assay and interassay precision, carry‐over, matrix effect, extraction recovery, and selectivity, for all analytes. Measurement uncertainties were also evaluated, and a decision rule was set with confidence for forensic purposes. The method may become suitable for clinical and forensic toxicology applications, taking advantage of the small matrix volume required, the simple and cost‐effective sample preparation procedure, and the fast analytical run time. Performances were monitored over a long‐term period and tested on 7620 driving under the influence of drugs (DUID) samples, including 641 positive samples.