Desenvolvimento e aplicação de sensores eletroquímicos modificados com óxido de grafeno reduzido e líquidos iônicos

Abstract

In this work, a study was developed for the detection of Nicotine (NIC) and Ciproflixacin (CPX), applying modified carbon paste electrodes with reduced graphene oxide (OGr) and the ionic liquids (LIs) 1-octyl-3-methylimidazolium hexafluorophosphate (OMIMPF6) and 1-butyl-3-methylimidazolium acetate (BMIMAc). All electrodes used are electroactive in relation to redox couple [Fe(CN)6] 3-/4- and also resulted in electrochemical responses for a CPX and a NIC. Modification percentages were evaluated, varying the proportions of OGr and LIs for the development of the modified electrode. The use of 10.0% OGr and 2.5% BMIMAc resulted in higher intensities of anode peak current for CPX, while the unmodified carbon paste electrode (EPC) showed better performance for a NIC. After that, studies were carried out to optimize the cell parameters (electrolyte, pH and preconcentration time) and technique parameters (scan rate, pulse amplitude and pulse time) for the detection of CPX. From the parameters optimized for CPX detection, an analytical curve was used from standard CPX solution, resulting in two dynamic linear concentration ranges. A range of interest corresponds to the detection of CPX with a concentration range of 6.99 x 10-9 to 6.95 x 10-7 mol L-1 (R2 = 0.9984), with a detection limit calculated at 4.21 x 10-9 mol L-1 and limit of quantification calculated at 1.28 x 10-8 mol L-1 . The application of the method in a commercial pharmaceutical sample shows a linear range with a concentration range of 4.99 x 10-8 to 1.57 x 10-7 mol L -1 (R2 = 0.9953). The reproducibility and repeatability calculated for EPCM/OGr-BMIMAc resulted in relative standard deviation values equal to 5.7% and 5.3%, respectively, ensuring the applicability of the developed analytical method.