Fast on-site screening of 3,4-methylenedioxyethylamphetamine (MDEA) in forensic samples using carbon screen-printed electrode and square wave voltammetry

Abstract

The worldwide seizures of illicit synthetic drugs have been dramatically increasing over the past decade, when the quantity of seized amphetamine-type stimulants (ATS) quadrupled, while seized ecstasy (3,4–methylenedioxymethamphetamine or MDMA)-like substances doubled. In this work, a simple and fast methodology for the electrochemical screening of ecstasy analogue MDEA (3,4-methylenedioxyethylamphetamine) in forensic samples is presented, for the first time, using a carbon screen-printed electrode (C-SPE) and square wave voltammetry (SWV). The electrochemical behavior of MDEA was studied by cyclic voltammetry at different pH values (2 to 12), where an altered electrochemistry of this drug on C-SPE, with an unreported redox pair, was observed in comparison with previous works dealing with the voltammetric detection of other ATS with similar chemical structures. Based on the acquired electrochemical processes, a redox reaction mechanism for MDEA on C-SPE is proposed. The best conditions (sensitivity and selectivity) for MDEA screening were obtained by SWV (a: 40 mV, f: 30 Hz, and Estep: 4 mV) and 0.04 mol L−1 Britton Robinson buffer solution at pH 3.0 as the supporting electrolyte. The proposed method presents a wide linear range (2.5 to 30.0 µmol L−1, R2 > 0.99), high sensitivity (0.569 µA / µmol L−1), low theoretical limit of detection (0.03 µmol L−1), and good repeatability using the same C-SPE (RSD < 6%; n = 10). The inter-device reproducibility (n = 5) showed a minimal variation of peak potentials (RSD < 2.3%). The interference study was performed with some adulterants usually found in ecstasy tablets, such as paracetamol, caffeine, glucose, ketamine, cocaine, acetylsalicylic acid, amphetamine (A), methamphetamine (MA), 3,4-methylenedioxyamphetamine (MDA), MDMA, ethylone (bk-MDEA), n-ethylpentylone (bk-EBDP) and dibutylone (bk-DMDBD). The method was applied in real seized samples containing MDEA with addition-recovery studies close to 100%. The developed method is promising to be used as a preliminary test for the screening of MDEA in the ever-changing situation concerning seized forensic samples. The proposed sensor exhibits attractive features for application in forensic analysis, such as rapidness, simplicity, low-cost, user friendly and portability.