A portable electrochemical method for cocaine quantification and rapid screening of common adulterants in seized samples

Abstract

A simple and robust batch-injection analysis system with square-wave voltammetric (BIA-SWV) detection is proposed for the determination of cocaine and screening of the most common adulterants (benzocaine, caffeine, lidocaine, phenacetin, paracetamol, and procaine) in seized cocaine samples. The sample only requires a dissolution step in electrolyte (0.1molL−1H2SO4) prior injection into the BIA cell. SWV scanning is performed after injection of the sample plug and cocaine and adulterants are electrochemically oxidized on a boron-doped diamond electrode (BDDE), resulting in a unique voltammetric profile. The use of BDDE was essential to achieve, for the first time, the electrochemical oxidation of cocaine in an acid medium. Using the optimized experimental conditions, a linear response was found for cocaine concentrations ranging from 6 to 30mgL−1, with a detection limit of 0.27mgL−1 (0.89μmolL−1). The accuracy of the proposed method was estimated by comparing the results obtained for seized cocaine samples by GC-FID and with the addition and recovery protocol. Furthermore, BIA with multiple pulse amperometric (MPA) detection is also proposed as a promising protocol for faster screening of seized cocaine samples.