Validation of an LC-MS/MS Method for the Quantification of 13 Designer Benzodiazepines in Blood

The misuse of designer benzodiazepines, as an alternative to prescription benzodiazepines and for drug-facilitated sexual assaults, has emerged as a growing threat, due in part to the ease of purchasing these drugs on the internet at low prices. Causing concern for safety is the lack of dosage information resulting in users self-medicating, often leading to unintended overdoses, coma or death at higher doses. With limited published data regarding the quantification of designer benzodiazepines in forensic cases, a method was validated for the determination of 13 designer benzodiazepines in postmortem blood, to add to the in-house method that already included a limited number of common designer benzodiazepines. The developed method included 3-hydroxyphenazepam, clobazam, clonazolam, delorazepam, deschloroetizolam, diclazepam, flualprazolam, flubromazepam, flubromazolam, flunitrazolam, meclonazepam, nifoxipam and pyrazolam in 0.5 mL postmortem blood using liquid chromatography-tandem mass spectrometry. The analytes were treated with solid phase extraction before undergoing separation on a C18 column and analyzed on the mass spectrometer in electrospray positive mode using multiple reaction monitoring. The linear range of the calibration curve was 1-200 ng/mL and up to 500 ng/mL for 3-hydroxyphenazepam, clobazam, flubromazepam and pyrazolam. The limits of detection and quantitation were 0.5 ng/mL (signal-to-noise ratio >3) and 1 ng/mL, respectively. The calculated bias, intra-day imprecision, relative standard deviation (RSD) and inter-day imprecision RSD were ±12%, 3-20% and 4-21%. Matrix effects ranged from -52% to 33% with RSD values ranging from 3-20%, indicating consistent effects throughout multiple sources. Recovery ranged from 35 to 90%, where only two compounds were <50%. Other parameters tested included carryover, stability, interference and dilution integrity, which all yielded acceptable results. With the application of this method to blood specimens from the New York City Office of Chief Medical Examiner, this validated method proved to be simple, reproducible, sensitive and robust.