Analytical Methodology for the Determination of Trace Metals in Biodiesel

The demand for energy resources by various systems such as production and transportation, as well as for physical comfort continues to grow apace, intensifying global dependence on fossil fuels and their derivatives. For this reason, numerous private and public programs in several countries have established feasible alternatives for the substitution of petroleum derivatives (Sahin, 2011; Saint ́Pierre et al., 2003). These alternatives are aimed at reducing dependence on imported and non-renewable energy, mitigating some of the environmental impacts caused by petroleum derivatives, and developing alternative technologies in the area of energy (Oliveira et al., 2002). Biodiesel has emerged as a promising alternative to petroleum, firstly because it promotes a qualitative and quantitative reduction of the emission of various air pollutants (Agarwai, 2005; López et al., 2005; Ilkilic  Behcet, 2010; Silva, 2010;) and secondly, as a strategic source of renewable energy to substitute diesel oil and other petroleum derivatives (Chaves et al., 2008; Jesus et al., 2008). Biodiesel, also known as vegetable diesel, is a fuel obtained from renewable sources, such as vegetable oils and animal fats, by means of chemical processes such as transesterification, esterification and thermal cracking (Chaves et al., 2010, Oliveira et al., 2009, Jesus et al., 2010; Arzamendi et al., 2008; Canakci et al., 1999; Meher et al., 2006). In chemical terms, biodiesel is defined as a mono-alkyl ester of long-chain fatty acids with physicochemical characteristics similar to those of mineral diesel. Because it is perfectly miscible and physicochemically similar to mineral diesel oil, biodiesel can be used pure or mixed in any proportions with other solvents in diesel cycle engines without the need for substantial or expensive adaptations (Ma  Hanna, 1999; Woods  Fryer, 2007). The literature highlights several important characteristics of biodiesel: (a) its market price is still relatively high when compared with that of conventional diesel fuel; (b) its content of sulfur and aromatic compounds is lower; (c) its average oxygen content is approximately 11%; (d) its viscosity and flashpoint are higher than those of conventional diesel; (e) it has a specific market niche directly associated with agricultural activities; and lastly, (f) in the case of biodiesel from used frying oil, it has strong environmental appeal (Nigam et al., 2011). The qualitative and quantitative reduction in the emissions of various air pollutants such as sulfur, particulate material, and particularly carbon, point to biodiesel as a promising