Desenvolvimento de sensores portáteis e de baixo custo a base de grafite para a determinação de analitos de interesse alimentício e farmacêutico

Abstract

In this work, two electrochemical platforms were developed for the manufacture of low-cost electrodes based on graphite, one supported on a glass capillary and the other on paper, with the sensors being applied in the analysis of analytes of food and pharmaceutical interest. The graphite electrode showed reproducibility of manufacturing, response, and performance superior to the commercial glassy carbon electrode, with 2.6 times greater analytical signal. An electrochemical treatment based on cyclic voltammetry was proposed to improve the electrode characteristics, and different media (acid, neutral and basic) were investigated. All the modifications significantly increased the response to the antibiotic ciprofloxacin, with a 43-fold increase in the basic medium compared to the untreated electrode. Scanning electron microscopy and Raman spectroscopy measurements revealed that this increase might be related to the exfoliation of graphene sheets at the electrode surface. A method by square wave voltammetry was developed for both electrodes with detection limits equal to 0.35 and 5.56 μmol L-1 for the treated and untreated electrodes, respectively. Both electrodes with and without treatment were applied to determine ciprofloxacin in drug, bovine milk, and water samples, the recovery values for the samples ranged from 80 to 116 %, indicating good accuracy of the method. The paper electrode presented affordable, simple manufacturing, and amenable to large-scale application since low-cost materials were used for this purpose. The applicability of the sensor was performed by determining sunset yellow and tartrazine, dyes widely used in the food industry with potentially toxic effects on humans. A differential pulse voltammetry method was developed for the simultaneous detection of analytes, with a linear range from 4 to 60 μmol L-1 and detection limits equal to 2.09 and 2.38 μmol L-1 for tartrazine yellow and sunset yellow, respectively. Samples of isotonic, powdered juice, juice, freeze pops, and gelatin were analyzed, and a simple dilution was performed.