Determination of cannabinoids in plasma using salting‐out‐assisted liquid–liquid extraction followed by LC–MS/MS analysis

Abstract The detection of the markers of Cannabis consumption in biological specimens is an important task for drug testing laboratories in varous contexts. A simple assay combining salting‐out assisted liquid–liquid extraction sample preparation and LC–MS/MS analysis was applied to the measurement of Δ9‐tetrahydrocannabinol, 11‐nor‐9‐carboxy‐Δ9‐tetrahydrocannabinol (THC‐COOH), 11‐hydroxy‐Δ9‐tetrahydrocannabinol, cannabinol and cannabidiol concentrations in 100 μl plasma specimens. The assay had linearity of 1–100 ng ml−1 for THC‐COOH and 0.5–50 ng ml−1 for the other tested cannabinoids. Assay validation criteria were fulfilled. Extraction yields (88.7–97.3%) and internal‐standard correct matrix effects (−9.6 to +5.4%) were acceptable. The assay was applied to 238 clinical specimens from trauma patients, with 19 samples presenting quantifiable concentrations of at least one of the target compounds. The developed assay is a simple and efficient strategy for simultaneous measurement of Δ9‐tetrahydrocannabinol, THC‐COOH, 11‐hydroxy‐Δ9‐tetrahydrocannabinol, cannabinol and cannabidiol concentrations in plasma specimens.