Abstract

3,4-methylenedioxymethamphetamine (MDMA) and 3,4-methylenedioxyamphetamine (MDA), called as “ecstasy”, are the main seized amphetamine-type stimulants consumed worldwide. Based on the voltammetric profiles of MDMA and MDA on 3D-printed carbon-black integrated polylactide, we propose a cyclic square-wave voltammetric (CSWV) approach to detect and discriminate both molecules in saliva and seized samples. CSWV combines enhanced sensitivity of pulsed techniques and mechanistic insights of cyclic voltammetry and herein we propose cyclic scans from 0.0 to +1.5 V and back to 0.0 V in Britton-Robinson buffer (0.12 mol L−1 pH=6.0). The first scan showed oxidation peaks at around +1.1 V for both MDMA and MDA, however, only MDMA showed a second oxidation peak at +1.35 V (stabilization of a cation radical). The reverse scan displayed a reduction peak only for MDA at around +0.2 V (the oxidation product from MDA is only electroactive in the reverse scan). Thus, MDMA can be selectively detected in the forward scan and MDA in the reverse scan. CSWV provided linear ranges from 5.8 to 35.0 µmol L−1 and 3.1 to 21.8 µmol L−1 (r2>0.99) for MDMA and MDA, respectively. Intra-day precision studies (n=10) showed that potential peaks (RSD<0.8%) and current intensity (RSD<3.8%) for all electrochemical processes are repetitive, with LODs lower than 1.8 µmol L−1. Paracetamol, caffeine, amphetamine, methamphetamine, ephylone, lysergic acid diethylamide and a phenethylamine drug (found in ecstasy-like tablets) did not interfere in the detection of MDMA and MDA. Analysis of seized tablets showed results similar to GC-MS. Spiked saliva samples were analyzed (recovery of 83-106%) after dilution in electrolyte. The combination of CSWV and 3D-printed electrodes (disposable devices easily produced in large scale at reduced cost) is highly promising for selective, fast, simple, low-cost, and on-site screening forensics analyses.

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