Methylone screening with electropolymerized molecularly imprinted polymer on screen-printed electrodes

Abstract Methylone (also known as bk-MDMA) is a substituted cathinone developed to elicit similar psychotropic effects as 4-methylenedioxymethamphetamine (MDMA, also known as ecstasy). Although methylone is a scheduled substance, its specific structural features means it generally cannot be detected and quantified using the same conditions commonly employed for ecstasy. This work therefore describes the development of an electroanalytical method for the selective quantification of methylone. This method uses an electropolymerized molecularly imprinted polymer (MIP) on the surface of screen-printed gold electrodes (SPAuEs), using 2-mercaptobenzimidazole (2-MBI) as the building monomer and methylone as the analyte template. The construction and optimization of the SPAuE-MIP sensor was studied, step-by-step, using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Additionally, the direct electrooxidation of methylone was investigated, and methylone-MIP interactions probed computationally. Ultimately, square-wave voltammetry (SWV) quantification of methylone using the SPAuE-MIP sensor was demonstrated to be both sensitive and selective. The electroanalytical determination showed suitable analytical parameters as: intra-day repeatability of 1.5%, a limit of detection (LOD) of 1.1 μmol L−1 (0.23 mg L−1) and a linear range up to 50 μmol L−1 (ca. 10 mg dL−1) with an r2 of 0.996, as well as much higher currents towards the analyte than similar compounds and commonly present interferents.