A fully validated LC–QTOF-MS screening workflow for the analysis of drugs in oral fluid.

This article focuses on the development and validation of a liquid chromatography–quadrupole time of flight tandem mass spectrometry (LC–QTOF-MS) method for screening multiple drugs in oral fluid collected with the Quantisal™ device, targeting compounds relevant to driving under the influence of drugs (DUID) investigations. The method meets or exceeds the National Safety Council's Alcohol, Drugs, and Impairment Division (NSC-ADID) recommended cut-off concentrations for both Tier 1 and Tier 2 drug classes, including novel psychoactive substances and Δ9-tetrahydrocannabinol (THC), using a single liquid–liquid extraction and a 10-minute chromatographic run. Validation followed ANSI/ASB forensic toxicology standards, demonstrating acceptable limits of detection, stability, interference, and matrix effects, with successful application to proficiency and authentic oral fluid samples. The LC–QTOF-MS approach offers advantages over traditional immunoassay screening by enabling broad-spectrum, retrospective data analysis without the need for immunoassay testing, although it currently excludes negatively ionized compounds such as barbiturates. This method represents the first validated LC–QTOF-MS screening procedure aligned with NSC-ADID recommendations for oral fluid in forensic toxicology.