Preparation of fatty acid methyl esters by direct transesterification of lipids with aluminium chloride-methanol.

A new and simple procedure has been developed that allows the direct transesterification of lipids, using aluminium chloride as a catalyst and methanol as the esterifying alcohol. The concentration of the salt and reaction conditions have been investigated for the different lipid classes. Comparative studies, performed with boron trifluoride-methanol, indicate that the same values are obtained when using either reagent. In addition, the method has been adapted for transesterification in the presence of silica gel and other adsorbents, thus allowing the preparation of fatty acid methyl or ethyl esters directly from samples previously fractionated by thin-layer chromatography. This new reagent is very stable and easy to handle, the fatty acids being generated in the same tube without further purification steps.