Electrochemical detection of mephedrone using a graphene screen-printed electrode: a new sensitive and selective...

Mephedrone (MEP) is an illicit stimulant drug that belongs to the synthetic cathinone (SC) class, which has been widely used for recreational purposes and reported in forensic analysis. The preliminary identification of MEP and other SCs in seized samples is of great interest for forensic investigation and a fast and simple screening test for these drugs would be useful for on-site and in-house analyses. In this study, we present the electrochemical detection of MEP in forensic samples using, for the first time, independent redox processes of SCs on a graphene screen-printed electrode (SPE-GP). The proposed method for MEP detection on the SPE-GP was optimized in Britton-Robinson buffer solution (0.1 mol L^-1) at pH 10.0 with adsorptive stripping differential pulse voltammetry (AdSDPV). The use of the SPE-GP with AdSDPV provides a wide linear range for MEP determination (2.6 to 112 μmol L^-1) with a low limit of detection (LOD) (0.3 μmol L^-1). The real surface area available for adsorption on the SPE-GP was estimated to be between 3.80 and 5.70 cm², which provided high sensitivity for the proposed method. Furthermore, good stability of MEP electrochemical responses on the SPE-GP was obtained using the same or different electrodes (N = 3), with relative standard deviation (RSD) < 5.0% for both redox processes. Interference studies for a common adulterant (caffeine) and twelve other illicit drugs (phenethylamines, amphetamines, and other SCs) were performed with a highly selective response for MEP detection. Therefore, the SPE-GP with AdSDPV is demonstrated to be a selective and sensitive screening method to detect MEP and other SCs in forensic analysis, providing a fast and simple preliminary identification of these drugs in seized samples.