Eletrodo de Pasta de Carbono Modificado com Nanopartículas de Hematita para a Determinação de Hidroquinona e Catecol em Meio Aquoso

Abstract

Due to their low degradation and high toxicity, the benzenediol isomers hydroquinone and catechol are considered environmental pollutants by both the United States Environmental Protection Agency (USEPA) and the European Union (EU), mainly found in wastewater from textile, pharmaceutical and chemical industries. In this context, due to the ability of iron oxides to act as good adsorbents or catalysts, its use in electrocatalytic studies may enable the making of electrodes, thus contributing to a positive outcome against the needs of monitoring emerging contaminants such as catechol and hydroquinone. In this work, modified carbon paste electrodes (MCPE) were obtained with hematite nanoparticles in ratios of 5%, 10% and 20% (m.m-1 ). Initially, all MPCE were electrochemically characterized by voltammetry and electrochemical impedance spectroscopy techniques using the redox probe [Fe(CN)6] -3/-4 , as well as hydroquinone and catechol. The MPCE showed electrochemical activity and mechanical stability in the investigated systems, besides making the redox process of the investigated systems more reversible and facilitating electron transfer on the electrode surface. Finally, the electroanalytical capacity of the MPCE with 5% (m.m-1 ) of hematite for hydroquinone and catechol in aqueous medium was evaluated. The analytical curves obtained from studies on both contaminants presented two linear ranges: i) from 0.1 µmol L -1 to 2 µmol L-1 , and ii) 2.5 µmol L-1 to 5 µmol L-1 , with detection and quantification limits of 0,05 µmol L-1 and 0,16 µmol L-1 for catechol, and 0,07 µmol L-1 and 0,22 µmol L-1 for hydroquinone, respectively. The electrode proved to be a sensitive electrochemical sensor for detecting the two organic contaminants, but enabling only the analysis of one of the isomers in the absence of the other, given the low sensor selectivity for simultaneous determination under the studied conditions.