Dados do Trabalho
MDMA OR MDA: COMBINED COLORIMETRIC AND ELECTROCHEMICAL SCREENING METHOD FOR SELECTIVE DETECTION OF AMPHETAMINE-TYPE STIMULANTS IN FORENSIC SAMPLES USING 3D-PRINTED ELECTRODES
The increasing number of seizures containing MDA and MDMA in association with other amphetamines demonstrates the importance of selective preliminary drug identification methods in the forensic scenario. Colorimetric tests, like Simon's and Marquis, are commonly used for fast screening of seizures. However, they are prone to produce false-positive and false-negative results due to similarities between molecules and/or the presence of other substances in different samples. Furthermore, high dye concentrations in colored tablets can affect the perception of color change, making colorimetric tests unreliable. Electrochemical methods have emerged as an option for forensic applications due to their selectivity, speed, simplicity, low cost, and potential for on-site data acquisition. In this scenario, disposable electrodes, produced at low cost by 3D printing, are an appealing alternative due to their portability, ability for large-scale production, and reduced risk of cross-contamination.
Selective detection of MDMA and MDA in forensic samples by both Simon's and electrochemical tests.
Simon's reagent was prepared with 1g of sodium nitroprusside, 100 mL of water, 2 mL of acetaldehyde and 2% w/v sodium carbonate. Britton-Robinson (BR) 0.1 M buffer solution pH 10.0 was used as supporting electrolyte. MDMA and MDA electrochemical detection was performed by DPV in a double cell with 3D printed working, counter, and pseudo-reference electrodes (partly covered with silver ink).
Resultados e Discussões
The presence of MDMA in the sample was suggested by the color change in the Simon's test (Fig. 1A) and by the appearance of two MDMA characteristics oxidations (O1 at +0.9 V, O2 at +1.1 V; Fig. 1B), as well as by the decrease in the Simon’s reagent oxidation peak (PSimon at +0.38 V).
MDA can be identified by its first oxidation (Pi at +0.6 V), since its second oxidation is at the same potential as the one from MDMA. Furthermore, the presence of MDA does not cause a decrease in PSimon peak. The proposed method showed a wide linear range (1 to 175 µM) and a limit of detection (LOD) of 0.1 µM for both analytes. These parameters are suitable for application to seized samples containing MDMA and MDA. In addition, good response stability was obtained using the same electrode (N = 10; RSD < 5%).
The combination of two techniques (Simon’s test and DPV) is a rapid and portable strategy for the selective and sensitive screening of MDMA and MDA in seized forensic samples.
Referências e agradecimentos
UFVJM, CAPES, CNPq, FAPEMIG, RMCF
Simon's test, 3D Printing, Voltammetry, MDMA, MDA.
Química e Toxicologia Forense
UFVJM - Minas Gerais - Brasil
LARISSA MAGALHAES DE ALMEIDA MELO, LUCAS VINICIUS DE FARIA, LUCIANO CHAVES ARANTES, EDUARDO MATHIAS RICHTER, RODRIGO ALEJANDRO ABARZA MUNOZ , WALLANS TORRES PIO DOS SANTOS