Combined colorimetric and electrochemical screening method using 3D printed devices: Towards the selective detection of MDMA in forensic samples

This study introduces a new approach that combines the benefits of colorimetric and electrochemical techniques for the selective detection of 3,4-methylenedioxymethamphetamine (MDMA) in forensic samples using a 3D-printed electrochemical device. We propose and implement a two-step strategy integrating Simon's test with differential pulse adsorptive stripping voltammetry (AdSDPV). Simon's test employs sodium nitroprusside, acetaldehyde, and sodium carbonate, while the electrochemical analysis is performed using AdSDPV on a 3D-printed graphite/polylactic acid (Gr/PLA) electrode in a dual-cell configuration. Initially, MDMA is identified by a color shift from pink to dark purple in Simon's test and is subsequently confirmed by observing changes in the electrochemical behavior on the 3D-printed Gr/PLA electrode, both before and after the colorimetric reaction. MDMA exhibits two characteristic oxidation processes: O-1 at +0.9 V and O-2 at +1.1 V (vs. Ag pseudo-reference). Following Simon's test, an additional oxidation process emerges with a distinct peak potential (P-Simon) at +0.38 V (vs. Ag pseudo-reference). Moreover, the peak currents of O-1 and O-2 decrease after the Simon's test reaction, further confirming the MDMA presence. The method demonstrates a broad linear range (1 to 175 mu M) and a low limit of detection (0.1 mu M) for MDMA. It achieves a good stability in electrochemical responses (RSD < 5 %) using either a single electrode (N = 5) or different electrodes (N = 3). The integrated approach, combining Simon's test and AdSDPV, effectively identifies MDMA, even in samples containing 3,4-methylenedioxyamphetamine (MDA). This method provides a robust, straightforward, and rapid selective screening tool for MDMA identification and quantification, leveraging three distinct responses: one colorimetric and two electrochemical (pre and post colorimetric reaction).