Portable electrochemical detection of illicit drugs in smuggled samples: towards more secure borders

Illicit drug consumption is posing critical concerns in our society causing health issues, crime-related activities, and the disruption of the border trade. The smuggling of illicit drugs such as cocaine and heroin in Europe urges the development of new tools for rapid on-site identification in cargos. Besides, the production of synthetic drugs increases internal trafficking, thus demanding simple and straightforward devices to detect illicit drugs in the field. Current methods used by law enforcement offices rely on presumptive color tests and portable spectroscopic techniques. However, these methods sometimes exhibit inaccurate results due to commonly used cutting agents or because the drugs are smuggled (hidden or mixed) in colored samples. Interestingly, electrochemical sensors can deal with these specific problems and can provide more reliable results in comparison to commercially available devices. Herein, it is presented an electrochemical device that uses low-cost screen-printed electrodes for the electrochemical detection of illicit drugs by square-wave voltammetry (SWV) profiling. A dual pH strategy based on a screening and a confirmatory test allows detecting the most encountered illicit drugs (i.e. cocaine, MDMA, heroin, amphetamine, and methamphetamine). The electrochemical interrogation of the illicit drugs exhibits the oxidation of the electroactive moieties in each drug at a certain potential, with the exception of amphetamine that uses an in situ derivatization to unravel its oxidation peak. A library of electrochemical profiles is built upon pure and mixtures of illicit drugs with common cutting agents. This library allows the design of a tailor-made script that shows the identification of each drug through a user-friendly interface. Finally, the results obtained from the analysis of different samples from confiscated cargos at different end-users sites present a promising alternative to current methods offering low-cost and rapid analysis in the field.