Screening of seized cocaine samples using electrophoresis microchips with integrated contactless conductivity detection

Abstract

This study describes the development of a new analytical method for the separation and detection of cocaine (COC) and its adulterants, or cutting agents, using microchip electrophoresis (ME) devices coupled with capacitively coupled contactless conductivity detection (C D). All the experiments were carried out using a glass commercial ME device containing two pairs of integrated sensing electrodes. The running buffer composed of 20 mmol/L amino-2-(hydroxymethyl) propane-1,3-diol and 10 mmol/L 3,4-dimethoxycinnamic acid provided the best separation conditions for COC and its adulterants with baseline resolution (R > 1.6), separation efficiencies ranging from (2.9 ± 0.1) to (3.2 ± 0.2) × 10 plates/m, and estimated LOD values between 40 and 150 μmol/L. The quantification of COC was successfully performed in four samples seized by the Brazilian Federal Police Department and all predicted values agree with values estimated by the reference method. Some other interfering species were detected in the seized samples during the screening procedure on ME-C D devices. While lidocaine was detected in sample 3, the presence of levamisole was observed in samples 2 and 4. However, their concentrations were estimated to be below the LOQ. ME-C D devices have proved to be quite efficient for the identification and quantification of COC with errors lower than 10% when compared to the data obtained by a reference method. The approach herein reported offers great potential to be used for on-site COC screening in seized samples.

Detection of fuel‐oxidizer explosives utilizing portable capillary electrophoresis with wipe‐based sampling

“…Overall, minimal carryover was observed across all experiments and the expected run time per sample is 40 s with an additional (2-3) min with positive identification. Further considerations in instrument portability could be explored, and many groups have utilized microfluidic electrophoresis coupled with C 4 D for the detection of relevant compounds for wipe-based sampling, e.g., illicit drugs [35,36]. However, a decrease in sensitivity could result using a microfluidic platform due the fast migration of inorganic anions [37].…”

Microfluidics: Innovations in Materials and Their Fabrication and Functionalization

“…Pinheiro et al carried out μCE of inorganic anions present in explosive residues with commercial glass microchips and contactless conductivity detection; however, the limit of detection of 2.5 μM was relatively high. Moreira et al developed an approach for the separation and detection of illicit drugs by using commercial glass μCE devices that contained two pairs of integrated sensing electrodes for contactless conductivity detection. This method has promise for on-site forensic investigation, provided analyte concentrations are >40 μM.…”

Lab-on-a-Chip approaches for the detection of controlled drugs, including new psychoactive substances: A systematic review

“…Aqueous samples offer advantages as these solutions can be representative of bulk or seized drug samples, and can be easily prepared by dissolving the analyte in solution. A variety of non-biological matrices were reported including water [20,34,36,[38][39][40][41][42], acetonitrile [25,29,34], phosphate buffered saline (PBS) [44][45][46][47], methanol [27,34], combination of acetone and deionised water [31], 2-(N-morpholino)ethanesulfonic acid (MES) buffer [48] well as beverages including energy drinks [37] and fruit juices [37] to represent 'spiked drink' samples. Only 7% of the publications using LOC devices tested powder drug samples.…”