1. Cocaine electrooxidation behavior, mechanism, and kinetics on a carbon paste electrode chemically modified with a cobalt or copper Schiff base complex
- Author
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Bruno Ferreira, Osmair Vital de Oliveira, Matheus Manoel Teles de Menezes, Aline Thaís Bruni, Edward R. Dockal, Alex Soares Castro, Marcelo Firmino de Oliveira, and Larissa Silva de Azevedo
- Subjects
Detection limit ,Schiff base ,chemistry.chemical_element ,Amperometry ,Pathology and Forensic Medicine ,Analytical Chemistry ,Carbon paste electrode ,VOLTAMETRIA ,chemistry.chemical_compound ,chemistry ,Materials Chemistry ,Chemical stability ,Physical and Theoretical Chemistry ,Cyclic voltammetry ,Law ,Voltammetry ,Cobalt ,Spectroscopy ,Nuclear chemistry - Abstract
Cocaine is one of the most abused drugs worldwide. Therefore, it is crucial to develop and improve cocaine identification techniques. This article describes two new electrodes chemically modified with ([Co((±)-t-3MeOsalcn)] or ([Cu((±)-t-3MeOsalcn)] and their use in free-base cocaine (FB) and cocaine hydrochloride (HC) identification. The electrodes were not active toward FB, but cyclic voltammetry analysis revealed an increase of 0.1 V (vs Ag/AgCl) (Eoxi) for HC. The square-wave voltammetry results showed that FB@([Cu((±)-t-3MeOsalcn)] and HC@([Cu((±)-t-3MeOsalcn)] presented higher amperometric sensitivity than FB@([Cu((±)-t-3MeOsalcn)] and HC@([Cu((±)-t-3MeOsalcn)]. The limit of detection (LOD) and the limit of quantification (LOQ) for FB@([Cu((±)-t-3MeOsalcn)] were 0.61 μmol.L−1and 2.04 μmol.L−1, respectively. As for HC@([Cu((±)-t-3MeOsalcn)] the LOD and the LOQ were 0.58 μmol.L−1 and 1.92 μmol.L−1, respectively. The higher chemical stability of the cocaine@([Cu((±)-t-3MeOsalcn)] complexes and the lower binding energy of FB and HC with ([Cu((±)-t-3MeOsalcn)] predicted by theoretical calculations explain the results of the voltammetric analyses. Moreover, the topographic and compositional results confirmed that HC adsorbed onto the surface of the electrodes chemically modified with [Co((±)-t-3MeOsalcn)] or ([Cu((±)-t-3MeOsalcn)]. Overall, our results demonstrated that the electrodes chemically modified with [Co((±)-t-3MeOsalcn)] or ([Cu((±)-t-3MeOsalcn)] developed in this study have promising application in cocaine detection and quantification. At the end of the study, we propose a schematic mechanism for the HC oxidation process at the modified electrodes.
- Published
- 2021