Desenvolvimento de sensor eletroquímico empregando eletrodo de carbono vítreo modificado com nanotubos de carbono e quantum dots (CdSe/CdS) para quantificação de ranitidina

Abstract

Medicines are substances that provide palliative, healing and preventive actions, as well as used in clinical diagnosis of diseases. However, its excessive use, improper disposal and reduced efficiency can cause deleterious effects for living beings. These effects are mainly attested through environmental analyzes and biological samples. Analytical methodologies are applied for such analyses, among them, chromatographic ones, such as HPLC and capillary electrophoresis analysis. However, electrochemical methods stand out because they have the ability to develop sensors that have good sensitivity, selectivity, stability, reasonable cost, in situ analysis capacity, possibility of miniaturization and generation of few residues. In this sense, in order to obtain a device with these improved characteristics, the present work addressed the development of an electrochemical sensor employing nanomaterials in glassy carbon electrode (ECV) with different modifying agents (chitosan + Au nanoparticles, multiwalled carbon nanotubes (MWCNTs) and CdSe, CdSe/CdS, ZnO nanoparticles) in order to quantify drugs, such as: captopril, flucloxacillin, amoxicillin, N-Acetyl-L-cysteine and ranitidine (RAN) in electrochemical analysis, through cyclic voltammetry (VC) and differential pulse voltammetry (DPV). The electrochemical responses obtained showed ranitidine as a alternative for analyte, and this choice was made due to user reports regarding its degradation, lack of information in the literature on electrochemical issues and the need for studies aimed at its drug quality. Given this information, modifications were made to the ECV using chitosan, in the absence and presence of nanoparticles (CdSe, CdSe/CdS, ZnO and Au), however, attenuation of the electrochemical response was observed. Thus, MWCNTs were applied with CdSe, CdSe/CdSe and ZnO nanoparticles, and the modification of NTC with CdSe/CdS was chosen, as it has one of the best sensitivities (44.45 I (µA) mmol-1 L). With the choice of modification, the optimization of chemical parameters was used, and these were: pH=7 for phosphate buffer at a concentration of 200 mM, with the following curve: Ipa (µA) = 44.45(± 0.36) CRAN (mM) - 0.17(± 0.01), linear range (F.L) = 7.0 - 56.6 µM, N = 7, r = 0.999, LD of 0.15 µM, LQ of 7.0 µM and MWCNTs:CdSe/CdS ratio of 1:0.5 (mg). In the morphological characterization, the SEM and Raman data demonstrated the presence of nanomaterials, as well as the maintenance of their structures. In the electrochemical characterization, the developed sensor showed an increase of 10% of the electroactive area in relation to the ECV without modification and as for the ranitidine oxidation process on the sensor surface, the combination of diffusion and adsorption processes was verified. EIS analysis was also employed, demonstrating a 66.5% reduction in the resistance at the electrode/solution interface of the modified sensor. Finally, the analysis of possible interferents did not show an RSD value greater than 5% and, in the recovery test with the presence of synthetic urine, the recoveries ranged from 98.3 to 102.8%. When applied in pharmaceutical formulations, such values were from 95.8 to 99.0%. Thus, demonstrating the potential of the chosen sensor for ranitidine determination.