Modificação de Eletrodos de Pasta de Carbono com Silsesquioxano e Ftalocianina de Níquel para Detecção Voltamétrica de Sulfanilamida

Inorganic compounds, as Nickel(II) Phthalocyanine (NiTsPc), have been widely applied in several fields of Chemistry because of its capacity to reduce the redox potentials of the reactions and for having good thermal and chemical stability [1-2]. Additionally, Silsesquioxane materials are reported as hybrid Organic-Inorganic compounds used in the manufacture of ion-selective membranes for electrodes [3-4]. Thus, this work describes the preparation, characterization and use of chemically modified carbon paste electrodes with 3-n-propyl(3-methylpyridinium) silsesquioxane chloride and Nickel(II) phthalocyanine-tetrasulfonic acid tetrasodium salt for the detection of sulfanilamide. Comparative analysis by Cyclic Voltammetry showed best response with the use of the electrode modified with Silsesquioxane and Phthalocyanine (CPE/Si3Pic+ Cl- /NiTsPc) in Ep at +0,93 V vs. Ag/AgCl, due to the electrostatic interactions between the silsesquioxane 3-pyridinium group and the sulfonic groups of the inorganic complex, which could facilitate electronic transfer and provide a better current signal. The material used in the preparation of the electrodes was characterized by Diffuse Reflectance Spectroscopy, which confirmed the interaction between Silsesquioxane and Phthalocyanine by bands B and Q of the complex. The study of scan rate showed an irreversible chemical process and diffusion-controlled reaction. The best current signal (i=0,80 µA) was obtained at pH 8 in Britton-Robinson buffer solution. The voltammetric technique chosen and optimized was Differential Pulse Voltammetry (DPV) due to its greater sensitivity to sulfanilamide. Under optimum conditions, the standard curve obtained for the sulfanilamide presented two linear ranges, from 14,0 µmol L-1 to 126,0 µmol L-1 (R = 0,99928) and from 126,0 µmol L-1 to 196,0 µmol L-1 (R = 0,99731). The limits of detection and quantification of the first linear range were 4,8 µmol L-1 and 14,5 µmol L-1 , respectively. This way, the proposed sensor may be applied for the determination of sulfanilamide, even as in medicinal, food or surface water matrices.