Separation of Acylglycerols from Biodiesel by High Performance Liquid Chromatography and Solid-Phase Extraction

In this study an alternative method was developed using a non-aqueous reversed phase high performance liquid chromatography (NARP-HPLC) to determine conversion and characterize the principal components of B100 biodiesel obtained from vegetable oils at several conversion rates. A novel solid-phase extraction (SPE) method with anninopropylsilane cartridges was proposed to enrich and separate the acylglycerols (mono-, di- and triacylglycerols) from B100 biodiesel. Soybean, corn, sunflower, cottonseed and canola oils were transesterified with methanol under reflux to different conditions, yielding 35 products which were submitted to investigation. The NARP-HPLC method was able to separate the fatty acid methyl esters (FAME) and the different classes of acylglycerols, making it an alternative for monitoring the conversion of different vegetable oils. In SPE, FAME elute selectively with n-hexane (reaching up to 100% recovery), whereas a fraction enriched (three- to six-fold) with the acylglycerols, elute subsequently with chloroform/methanol 2:1. The separation of the fractions of EsMAG and acylglycerols should contribute to the chemical characterization of the B100 for several analytical techniques. The combination of NARP-HPLC and SPE could be a new starting point for monitoring the quality of biodiesel, for the isolation of acylglycerols and for the production of reference materials.