Uso de eletrodos impressos para determinação de metais e antioxidante em combustíveis fósseis e renováveis empregando técnicas eletroanalíticas

Abstract

This thesis demonstrates the potential application of disposable electrodes to monitor some parametrs of the quality control of fossil and renewable fuels. It was used a screenprinted gold electrode (SPGE) for determining traces of lead, copper and mercury in bioethanol and lead in aviation fuel (gasoline, kerosene and bio-kerosene) and screen-printed graphite electrodes (SPGphE) to determine the antioxidant 2,6-di-tert-butylphenol (2,6- DTBF) in aviation kerosene (jet fuel) and biodiesel. For the determination of metals in bioethanol and the antioxidant in biodiesel and jet fuel, the samples were just diluted in electrolyte before the electrochemical analysis, presenting a low LOD (~ 1 mg L-1) for a deposition time of 240s (-0.5 V) and satisfactory recovery values (96-104%) for spiked samples. For Pb detemination in aviation fuel, two sample preparation procedures were used: dry-ashing and digestion assisted by ultrasound. It was also demonstrated some advantages of applying the BIA technique associated with electrochemical analysis (amperometric and stripping voltammetry). For the determination of metal in ethanol, one SPGE can be used up to 15 analytical measurements. To Pb determination in aviation fuels, one SPGE can be applied for 60 consecutive measurements for ultrasound treated samples and 120 measurements for dry-ashed samples. Due to the different preparation procedures of the samples and dilutions, different LOD values for Pb were obtained, 7.1 and 0.8 ng g-1 for ultrasound-treated and dry-ashing, respectively. Even dry-ashing presenting lower LOD, the treatment assisted by ultrasound was faster and safer. On the other hand, the SPGphE can be applied to hundreds of samples (more than 200 injections) in the determination of the antioxidant in aviation fuel and biodiesel. The method is rapid (~ 9 s of injection) and precise (RSD = 2.5%, n = 10) and the results were statistically consistent with the results obtained by chromatographic analysis. All presented analytical systems show great promise for portable analysis, considering that there are portable potentiostats, BIA cells (developed for screenprinted electrodes) and battery-powered electronic micropipettes.