Desenvolvimento de sensor eletroquímico baseado em grafeno para a determinação de antioxidantes em biocombustíveis

Abstract

The use of alternative sources for fuel production has been gaining attention in recent years. Biodiesel has been standing out despite its low stability to oxidation, which can be minimized by the use of antioxidants as additives added to slow down these processes. The central aim of this work is to develop low-cost electrochemical sensors using graphene electrodes produced by CO2 laser etching. Polyimide is an excellent material for generating Laser Induced Graphene surfaces (known as laser Induced Graphene Electrode, LIGE) which have adequate stability, robustness and sensitivity. CO2 laser cutter (or engraver) and polyimide sheet were used to manufacture the electrodes, which demonstrated that LIGE's can be used to electroanalyse tert-butylhydroquinone (TBHQ), which is an antioxidant used in biodiesel. The oxidation of TBHQ was optimized by differential pulse voltammetry technique, its oxidation occurred at positive potentials (Epa = 0.05 V vs. Ag|AgCl|KCl(sat.)) in 0.12 mol L-1 Britton-Robinson buffer solution pH 6.0 which was selected to perform the remaining experiments. The sensor showed a linear range from 5 to 450 μmol L-1 (r > 0.9989) and an estimated detection limit of 2.7 μmol L-1. Metal species such as Fe3+, Mn2+, Cr2+, Zn2+ and Pb2+ did not statistically interfere in the determination of TBHQ, except Cu2+ which interfered and corrected by applying EDTA as a sequestrator. Finally, the TBHQ-enriched biodiesel samples were analyzed and recovery values ranging from 87.6 to 105.9% were obtained, showing no sample matrix effects. In conclusion, the applicability of LIGE for TBHQ sensing in real biodiesel samples is verified.