Determinação voltamétrica de chumbo(II) e cobre(II) em biodiesel microemulsionado usando o eletrodo de diamante dopado com boro

Abstract

Biodiesel is a renewable source fuel that allows us to promote a more sustainable future, being an alternative to the current fuels derived from petroleum. Therefore, we need to inspect the same to ensure its quality, since the presence of contaminants can reduce the effectiveness of this fuel. Currently, the main methods used in the analysis of biodiesel quality are spectrometric methods, due to their high-resolution power. However, there is a search for substitutes that have low cost and comparable sensitivity, we can highlight the voltammetric methods. Among the voltammetric techniques we can emphasize the SWASV (Square Wave Anodic Stripping Voltammetry), which has similar sensitivity to the widely used techniques, besides having a low maintenance cost. In this context, this paper describes a methodology using the SWASV associated to a DDB (boron doped diamond) electrode for the determination of Pb(II) and Cu(II) in microemulsified biodiesel. Thus, the experimental parameters of SWASV were optimized in order to obtain maximum efficiency in the technique. So, the optimization of the preconcentration stage obtained an optimum value of -1.20 V for the preconcentration potential and 210 s for the deposition time of both metals. In the scanning stage, 20 Hz and 50 mV optimum values were defined as frequency and amplitude respectively, with a linear work range of 2.0 × 10-8 to 1.0 × 10-7 mol L-1. This procedure was applied in biodiesel samples of corn oil, allowing to find a LOD (Limit of Detection) of 2.7 × 10-8 mol L-1 for lead and 4.0 × 10-9 mol L-1 for copper, and LOQ (Limit of Quantification) of 9.2 × 10-8 mol L-1 for Pb (II) and 1.3 × 10-8 mol L-1 for Cu (II). In this way, we can conclude that this new methodology is a viable and robust tool for simultaneous determination of metals in biodiesel, allowing fast and sensitive analyzes in non-aqueous systems.