The determination of cocaine, benzoylecgonine, and cocaethylene in small-volume oral fluid samples by liquid chromatography-quadrupole-time-of-flight mass spectrometry

A quantitative analysis was developed for the determination of cocaine, benzoylecgonine, and cocaethylene in oral fluid using liquid chromatography-tandem mass spectrometry. After internal standardization and solid-phase extraction, chromatographic separation was achieved on a reversed-phase column by gradient elution. The reconstructed mass chromatograms of the collision-induced dissociation transitions of m/z 290 → m/z 168 (benzoylecgonine), m/z 304 → m/z 168+119 (2′-methylbenzoylecgonine), m/z 304 → m/z 182 (cocaine), m/z 318 → m/z 196 (cocaethylene), and m/z 318 → m/z 182+119 (2′-methylcocaine) were used for quantitation. The developed method was adequately validated. Good linearity was obtained from 10 to 1000 μg/L. Extraction recoveries exceeded 85% for all compounds. Excellent total and within-run reproducibilities (CV% < 20%) and accuracy figures were obtained. The limit of detection (signal-to-noise ratio ≥ 3) was 1 μg/L for all three compounds. As such, a method for drug abuse confirmation analysis in oral fluid, compatible with the present day saliva collecting devices, is obtained. The method was applied to real samples (n = 15) obtained from suspected drug users, of which seven proved positive. The concentrations found in the positive samples were between 10.2 and 200.6 pg/L for cocaine, < limit of quantification (LOQ) and 10.5 μg/L for cocaethylene, and < LOQ and 59.2 μg/L for benzoylecgonine.