Screening and confirmatory method for benzodiazepines and hypnotics in oral fluid by LC-MS/MS

A procedure is presented for the screening of 17 benzodiazepines and hypnotics in oral fluid after collection with the Intercept® device by LC-MS/MS (alprazolam, 7-aminoclonazepam, 7-aminoflunitrazepam, bromazepam, clobazam, diazepam, lorazepam, lormetazepam, midazolam, nordiazepam, oxazepam, temazepam, tetrazepam, triazolam, zaleplon, zopiclone and zolpidem). The method involves extraction of 0.5 mL of oral fluid (previously stored in the Intercept blue buffer) treated with 0.5 mL of phosphate buffer (pH 8.4) in the presence of 5 ng diazepam-d5 used as internal standard, with 3 mL of diethyl ether/methylene chloride (50/50) and separation using liquid chromatography-tandem mass spectrometry. The limits of quantification for all benzodiazepines and hypnotics range from 0.1 to 0.2 ng/mL. Linearity is observed from the limit of quantification of each compound to 20 ng/mL (r2 > 0.99). Coefficients of variation at 2 ng/mL, measured on 6 points range from 4 to 8% for all drugs, except zopiclone (34%). Extraction recovery, measured at the same concentration was higher than 90%. Ion suppression was evaluated for each compound and was lower than 10% for all drugs except zopiclone (93%). These results were found suitable to screen for 17 benzodiazepines in oral fluid and detect them at very low concentrations, making this method suitable for monitoring subjects under the influence.