EVALUATION OF THE RELATIVE PROTECTION FACTOR OF ROSEMARY EXTRACT IN BIODIESEL IN THE PRESENCE OF TRANSITION METAL IONS

Abstract

Biodiesel contains unsaturated methyl esters making it susceptible to oxidation reaction. Among the factors that cause oxidative instability is the contamination by transition metal ions that in small quantities catalyze the oxidation reaction. The objective of this work was to evaluate the relative protection factor of rosemary extract, in biodiesel, in the presence of transition metal ions. Chromatographic analysis and characterization of biodiesel were performed as well as the quantification of total phenolic compounds and extract activity. The ions Cr 3+ , Co 2+ and Fe 2+ , at a concentration of 3.95 x 10 -3 mol L -1 , were added to the biodiesel with and without rosemary extract. The samples were submitted to the Rancimat test and to infrared region analyses. The infrared region spectra of the samples with Cr 3+ are in accordance with the least catalytic power of this ion under the biodiesel oxidation. Samples with Co 2+ ions, without extract, presented bands of aldehydes, and samples with Fe 2+ ions show the formation of peroxide radicals, without rosemary extract at 48h. The antioxidant effect of the extract in biodiesel is observed by the reduction of the induction period of the samples. The relative protection factor proved to be a good tool to evaluate its efficiency.