Estudo eletroquímico dos efeitos de líquidos iônicos apróticos e próticos em eletrodos modificados

Abstract

In the last two decades, there has been a significant increase in the use of ionic liquids (ILs), with possibilities for application in different areas. The various combinations of cations and anions to form compounds suitable for specific applications made ILs potential for different applications, such as common solvents, appreciable electrolytes, among others. The use of ILs as electrode modifiers has been reported intensely due to the significant contribution of these compounds in terms of intensity and selectivity for electrochemical applications. Ionic liquids based on imidazole cations and with anions [PF6] - and [BF4] - are the most found in the literature, while applications of ILs with other anions are quite limited. In this work, the ILs 1-ethyl-3-methylimidazolium thiocyanate (EMImSCN), 1-ethyl-3-methylimidazolium acetate (EMImAc), 1-butyl-3- methylimidazolium acetate (BMImAc) and 2-hydroxyethylammonium acetate (2- HEAA), were investigated as potential carbon paste electrode modifiers (MCPE-ILs) applied in the detection of the carbendazim fungicide in Britton-Robinson (BR) buffer, using the differential pulse voltammetry technique. The parameters such as electrolyte pH, pre-concentration time, scan rate, pulse time and pulse amplitude that influence the voltammetric response have been optimized. The precision of the developed method showed satisfactory results of repeatability and reproducibility for MCPE/EMImAc, MCPE/BMImAc and MCPE/2-HEAA (DPR <11%), being within the limit accepted by ANVISA and INMETRO for low concentrations (0.05 µmol L-1 ). The selectivity of the method performed for MCPE/2-HEAA revealed a low variation in the intensity of the anodic peak current of CBZ, less than 7.5%, in the investigated proportions of the interfering species. The analytical curve for MCPE/2-HEAA showed a linear range from 0.009 to 0.476 µmol L-1 (R2 = 0.9964) and limits of detection (1.68 nmol L-1 ) and quantification (5.63 nmol L-1 ). The sensor modified with 2-HEAA was applied to the grape juice sample, obtaining satisfactory recovery results (100.60; 106.71 and 113.51%) from CBZ, using the standard addition method. The partial validation of the method showed that the MCPE/2-HEAA sensor has an excellent capacity to be used in the quantification of low concentration CBZ.