Development of fast analytical procedures for biodiesel quality control

Abstract

Restrictive quality parameters for biodiesel have been established because of its worldwide use as a fuel. This aims to assure the performance, to avoid damages to the motors and minimize environmental impacts. These parameters include (i) the oxidative stability, directly related to amount of unsaturated alkyl esters, which can be estimated by the iodine index and (ii) the sulfur content, mainly found as sulfate. However, the analytical procedures for determination of these species are laborious and time-consuming. This project aims to develop fast and reliable analytical procedures for determination of iodine index and sulfate in biodiesel. The former will be determined by addition of an alcoholic iodine solution to the biofuel for reaction with the unsaturated species. The remaining fraction will be then extracted to the aqueous phase by an iodide solution. The triiodide concentration will be determined by spectrophotometry and the absorbance is expected to be inversely proportional to the iodine index. Extraction to an aqueous phase and precipitation with Ba(II) will be exploited for sulfate determination. The remaining fraction of the cation will be determined by flame atomic absorption spectrometry and related to the sulfate concentration in the sample. These research proposals will be evaluated with two different approaches: (i) single vessel procedures aiming to simplify the analytical protocol and make feasible at line in situ analysis and (ii) flow-based procedures exploiting the lab-in-syringe process for mechanization and reproducible exploitation of incomplete extractions and reactions. The analytical procedures exploiting both strategies will be critically compared and accuracy will be assessed by comparison of the results obtained by reference procedures by considering biodiesel from diverse feedstocks.