Caracterização eletroquímica e espectroscópica da interação cobre-carbaril em meio aquoso
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Data
2023-12-21
Autores
Silva, Helia Aparecida [UNIFESP]
Orientadores
Akamatu, Eliana Maira Agostini Valle [UNIFESP]
Tipo
Dissertação de mestrado
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Resumo
Pesticidas são substâncias utilizadas no combate a diferentes tipos de pragas em plantações e armazenamento de alimentos. O carbaril é um inseticida da classe dos carbamatos muito utilizado no combate a pragas em plantações de banana, abacaxi, tomate, entre outros. Por apresentar em sua estrutura átomos de nitrogênio e oxigênio, com pares de elétrons disponíveis, pode interagir com íons metálicos presentes no ambiente, formando novos compostos, podendo modificar suas propriedades. Para compreender melhor o tipo de interação que ocorre entre o carbaril e os íons metálicos em solução, neste trabalho foi avaliada a interação entre o íon metálico cobre (II) e o pesticida carbaril, utilizando técnicas eletroquímicas e espectroscópicas. Por medidas de voltametria cíclica, observou-se o deslocamento do pico de oxidação do cobre. Por espectroscopia UV-Vis observou-se a variação nas bandas de absorção do ligante quando em presença de metal. A medida de Ressonância Magnética Nuclear nos mostrou variação do sinal em 3,55 ppm, referente ao hidrogênio ligado ao nitrogênio da amida da molécula de carbaril, após a adição de cobre à solução. Isso nos sugere que a interação entre as espécies ocorre por meio deste nitrogênio. Variações também foram observadas nas medidas de espectroscopia de absorção na região do infravermelho, com o surgimento de um novo estiramento com número de onda em 567 cm-1 o qual foi atribuído a interação metal-nitrogênio. Medidas de cromatografia gasosa também foram realizadas e observou-se a variação do tempo de retenção referente ao carbaril em 10,095 minutos e o surgimento de um novo tempo de retenção em 29,311 minutos. Observou-se nos espectros de massa o surgimento de um pico base de 296 m/z sendo, possivelmente, a massa do novo composto. Os resultados obtidos nos indicam que ocorre interação entre o carbaril e o íon metálico cobre em meio aquoso. Esses dados são importantes para compreender, futuramente, a toxicidade desse novo composto formado.
Pesticides are substances used to combat different types of pests in crops and food storage. Carbaryl is a carbamate class insecticide widely used to combat pests in banana, pineapple, tomato plantations, among others. Because its structure contains nitrogen and oxygen atoms, with pairs of electrons available, it can interact with metallic ions present in the environment, forming new compounds and modifying their properties. To better understand the type of interaction that occurs between carbaryl and metallic ions in solution, in this work the interaction between the metallic ion copper (II) and the pesticide carbaryl was evaluated, using electrochemical and spectroscopic techniques. Using cyclic voltammetry measurements, the shift of the copper oxidation peak was observed. Using UV-Vis spectroscopy, the variation in the ligand's absorption bands was observed when in the presence of metal. The Nuclear Magnetic Resonance measurement showed us a variation in the signal of 3.55 ppm, referring to the hydrogen linked to the amide nitrogen of the carbaryl molecule, after the addition of copper to the solution. This suggests to us that the interaction between species occurs through this nitrogen. Variations were also observed in absorption spectroscopy measurements in the infrared region, with the appearance of a new stretch with a wave number at 567 cm-1 which was attributed to the metal-nitrogen interaction. Gas chromatography measurements were also carried out and a variation in the retention time for carbaryl was observed at 10.095 minutes and the emergence of a new retention time at 29.311 minutes. The appearance of a base peak at 296 m/z was observed in the mass spectra, possibly the mass of the new compound. The results obtained indicate that interaction occurs between carbaryl and the copper metal ion in an aqueous medium. These data are important to understand, in the future, the toxicity of this new compound formed.
Pesticides are substances used to combat different types of pests in crops and food storage. Carbaryl is a carbamate class insecticide widely used to combat pests in banana, pineapple, tomato plantations, among others. Because its structure contains nitrogen and oxygen atoms, with pairs of electrons available, it can interact with metallic ions present in the environment, forming new compounds and modifying their properties. To better understand the type of interaction that occurs between carbaryl and metallic ions in solution, in this work the interaction between the metallic ion copper (II) and the pesticide carbaryl was evaluated, using electrochemical and spectroscopic techniques. Using cyclic voltammetry measurements, the shift of the copper oxidation peak was observed. Using UV-Vis spectroscopy, the variation in the ligand's absorption bands was observed when in the presence of metal. The Nuclear Magnetic Resonance measurement showed us a variation in the signal of 3.55 ppm, referring to the hydrogen linked to the amide nitrogen of the carbaryl molecule, after the addition of copper to the solution. This suggests to us that the interaction between species occurs through this nitrogen. Variations were also observed in absorption spectroscopy measurements in the infrared region, with the appearance of a new stretch with a wave number at 567 cm-1 which was attributed to the metal-nitrogen interaction. Gas chromatography measurements were also carried out and a variation in the retention time for carbaryl was observed at 10.095 minutes and the emergence of a new retention time at 29.311 minutes. The appearance of a base peak at 296 m/z was observed in the mass spectra, possibly the mass of the new compound. The results obtained indicate that interaction occurs between carbaryl and the copper metal ion in an aqueous medium. These data are important to understand, in the future, the toxicity of this new compound formed.