Experimental and Theoretical Investigation of Flunitrazepam Electrochemical Behavior on Screen-Printed Electrodes: Low-Cost Strategy for Forensic Applications

The issue of drink spiking has attracted considerable worldwide attention, generating widespread public concern and fear. This practice entails the unsuspecting or willing ingestion of a substance that has been secretly introduced into a beverage. Flunitrazepam (FLU) is an important drug used for this purpose. Herein, commercial screen-printed electrodes (SPEs) were used for detecting FLU in spiked beverage samples (mineral water, beer, red wine, Brazilian sugarcane and jambu spirit, and cashew juice). Computational methods revealed that the interaction between the analyte and the working electrode surface occurs through dispersion, applying the third-order Self-consistent Charge Density Functional Tight-Binding (SCC-DFTB) methodology. Under optimized square wave voltammetry (SWV) conditions, linear range from 4.8 to 14.4 mg L⁻¹ and limits of detection (LOD) and quantification (LOQ) values were obtained at 0.01 and 0.04 mg L⁻¹, respectively. Recovery values (80%–85%) for FLU in sugarcane and jambu spirit samples, achieved through the standard addition method, attested the high performance of proposed method.