Electrochemical detection of MDMA and 2C-B in ecstasy tablets using a selectivity enhancement strategy by in-situ derivatization

A two-step electrochemical sensor distinguishes between the drugs MDMA and 2C-B. In the first step, direct electrochemical analysis detects MDMA, but testing over 70 substances showed that 2C-B was the only common drug producing a false positive for MDMA. The second step uses formaldehyde to chemically modify 2C-B, creating a distinct electrochemical signal that differentiates it from MDMA. Testing on 71 ecstasy tablets seized by the Amsterdam Police, the sensor correctly identified all 39 MDMA-containing tablets and 10 of 11 tablets containing 2C-B. It also worked on dark-colored tablets where spectroscopic and colorimetric tests failed.

Study at a glance

Abstract

Forensic drug laboratories are confronted with increasing amounts of drugs and a demand for faster results that are directly available on-site. In addition, the drug market is getting more complex with hundreds of new psychoactive substances (NPS) entering the market in recent years. Rapid and on-scene presumptive drug testing therefore faces a shift from manual colorimetric tests towards approaches that can detect a wider range of components and process results automatically. Electrochemical detection offers these desired characteristics, making it a suitable candidate for on-site drug detection. In this study, a two-step electrochemical sensor is introduced for the detection of MDMA and 2C-B. Firstly, a direct electrochemical analysis was performed to detect MDMA. Validation experiments on over 70 substances revealed that 2C-B was the only frequently encountered drug that gave a false positive result for MDMA in this first analysis. A second step using in-situ derivatization was subsequently introduced. To this end, formaldehyde was used for N-methylation of 2C-B thereby enhancing its electrochemical profile. The enriched electrochemical fingerprint in the second step allowed for clear differentiation between MDMA and 2C-B. The applicability of this approach was demonstrated with 71 ecstasy tablets seized by the Amsterdam Police. The MDMA/2C-B sensor correctly identified all 39 MDMA-containing tablets and 10 out of 11 tablets containing 2C-B. Most notably, correct results were also obtained for dark colored tablets in which both spectroscopic analysis and colorimetric tests failed due to obscured signals.