Detection and validated quantification of 21 benzodiazepines and 3 "z-drugs" in human hair by LC-MS/MS

A method for detection and quantification of 21 benzodiazepines and the pharmacologically related "z-drugs" in human hair samples was developed and fully validated using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). After methanolic and methanolic/aqueous extraction, the analytes were separated using two different LC-MS systems (AB Sciex 3200 QTRAP and AB Sciex 5500 QTRAP). Separation columns, mobile phases and MS modes for both systems were: Phenomenex Kinetex, 2.6 μm, 50/2.1; 5mM ammonium formate buffer pH 3.5/methanol, total flow 0.75 mL/min; electrospray ionization (ESI), multiple reaction monitoring (MRM), information dependent acquisition (IDA), enhanced product ion scan (EPI). The assays were found to be selective for the tested compounds (alprazolam, 7-aminoclonazepam, 7-aminoflunitrazepam, bromazepam, chlordiazepoxide, clonazepam, N-desalkylflurazepam, diazepam, flunitrazepam, flurazepam, alpha-hydroxymidazolam, lorazepam, lormetazepam, midazolam, nitrazepam, nordazepam, oxazepam, phenazepam, prazepam, temazepam, triazolam, zaleplon, zolpidem and zopiclone), all validation criteria were in the required ranges according to international guidelines, except for bromazepam. Matrix effects, and process efficiencies were in the acceptable ranges evaluated using the post-extraction addition approach. Lower limits of quantification were between 0.6 and 16 pg/mg of hair. The LC-MS/MS assay has proven to be applicable for determination of the studied analytes in human hair in numerous authentic cases (n=175).