Rapid Drop-Volume Electrochemical Detection of the “Date Rape” Drug Flunitrazepam in Spirits Using a Screen-Printed Sensor in a Dry-Reagent Format

Abstract

Flunitrazepam is an extremely potent benzodiazepine sedative which is associated with “drug-facilitated sexual assault” when administered within an alcoholic drink. This work describes a simple electrochemical method for on-site rapid detection of flunitrazepam in untreated spirits (whiskey, vodka and gin) using a single-use screen-printed sensor (featuring graphite working and auxiliary electrodes and an Ag/AgCl reference electrode) in a dry reagent format. Analysis was performed by placing a drop of sample on the sensor, which was previously coated with dry KCl, and recording selected reduction/oxidation peaks of the target compound in a cyclic voltammetry scan. The limit of quantification of flunitrazepam was at the sub-mg L−1 range. The between-sensor % relative standard deviation of the analytically useful reduction peak in a solution containing 11.4 mg L−1 flunitrazepam was 9.8% (n = 5). Quantification was performed using calibration curves constructed from pooled samples spiked with flunitrazepam with relative errors <15%. The main advantages of the methodology are that it involves no sample pretreatment (such as deoxygenation, extraction or reagent(s) addition) and requires only drop-sized volumes of the sample, thus facilitating rapid on-site screening using portable equipment.