3,4-Methylenedioxypyrovalerone (MDPV) Sensing Based on Electropolymerized Molecularly Imprinted Polymers on Silver Nanoparticles and Carboxylated Multi-Walled Carbon Nanotubes.

3,4-methylenedioxypyrovalerone (MDPV) is a harmful and controlled synthetic cathinone used as a psychostimulant drug and as sport-enhancing substance. A sensor was developed for the direct analysis of MDPV by transducing its oxidation signal by means of an electropolymerized molecularly imprinted polymer (e-MIP) built in-situ on the screen-printed carbon electrode's (SPCE) surface previously covered with multi-walled carbon nanotubes (MWCNTs) and silver nanoparticles (AgNPs). Benzene-1,2-diamine was used as the functional monomer while the analyte was used as the template monomer. Each step of the sensor's development was studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in a solution containing ferricyanide, however no redox probe was required for the actual MDPV measurements. The interaction between the poly(o-phenylenediamine) imprinted polymer and MDPV was studied by density-functional theory (DFT) methods. The SPCE-MWCNT-AgNP-MIP sensor responded adequately to the variation of MDPV concentration. It was shown that AgNPs enhanced the electrochemical signal by around a 3-fold factor. Making use of square-wave voltammetry (SWV) the developed sensor provided a limit of detection (LOD) of 1.8 µmol L-1. The analytical performance of the proposed sensor paves the way to the development of a portable device for MDPV on-site sensing to be applied in forensic and doping analysis.

The Analytical Challenge in the Determination of Cathinones, Key-Players in the Worldwide Phenomenon of Novel Psychoactive Substances.

Since the turn of the century, the synthesis, availability, and use of new psychoactive substances (NPS) have been increasingly reported worldwide, being considered a complex global phenomenon. As most NPS are not detected in routine drug screening, extra efforts have been made to develop new analytical methods for the detection of these compounds, with several approaches being successfully applied and reported in the literature. The increased traffic of NPS is often related to the limited capacity for detecting and monitoring these compounds, which makes it essential to explore in detail both conventional and more recent approaches to prospect novel sensing strategies and develop in-the-field sensors that are able to detect NPS in a time-efficient manner, within a wide range of concentrations, and in a variety of sample matrices, such as biological samples, wastewater, powders, crystals, and post-mortem specimens. In this context, this review aims to provide an overview of the state of the art in the identification and analytical detection of cathinones, a considerable group within NPS, as well as a critical discussion of the most frequently described sample preparation techniques.