High-throughput screening of cocaine, adulterants, and diluents in seized samples using capillary electrophoresis with capacitively coupled contactless conductivity detection

Abstract

Cocaine is one of the most frequently used illicit drug in the world. Therefore, the development of simple and fast methods for the detection of cocaine and common adulterants, diluents and impurities are extremely important in forensic investigations. The present study describes, for the first time, a method based on capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D) for the rapid (2.5 min) and simultaneous quantification of cocaine, levamisole, lidocaine, carbonate, borate, chloride, nitrate, nitrite and sulphate. In the experiment, anions were separated in co-electroosmotic mode and cations in counter-electroosmotic mode employing a buffer solution composed by 10.0 mmol L−1 TAPS, 12 mmol L−1 NaOH and 0.2 mmol L−1 CTAB as the background electrolyte (pH = 8.8). The developed CE method demonstrated some interesting analytical characteristics such as: (i) a simple sample pretreatment step (only dilution in water and filtering), (ii) high-throughput screening (24 injections h−1), (iii) proper recovery values (between 72 and 118%), and (iv) an inter-day precision of less than 7% for all analytes. The procedure was successfully applied in the analysis of seized cocaine samples collected by the Integrated Forensics Post (PPI) of the Minas Gerais Civil Police (Uberaba, Minas Gerais State, Brazil), during the year of 2018.