Separation of lipid classes by solid phase extraction.

A rapid and reliable method for the separation of lipid classes is described using aminopropyl disposable columns. This method is a modification to an existing procedure that allows the separation of both neutral and acidic phospholipid fractions and a high recovery of the latter. Acidic phospholipids were eluted with a mixture of hexane-2-propanol-ethanol-0.1 M ammonium acetate-formic acid 420:350:100:50:0.5 containing 5% phosphoric acid after neutral phospholipids had been eluted with methanol. It was verified that extremely high recoveries of cholesterol (CH), triglycerides (TG), free fatty acids (FFA), phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidic acid (PA), sphingomyelin (SM), and cerebrosides were obtained with this method. In addition, there appeared to be no preferential losses or degradation of any particular molecular species as the fatty acid distribution of bovine brain PS and the molecular species profile of plant PI were unaltered by the procedure. Depending on the tissue, this method may yield fractions containing pure lipid classes and/or simple mixtures of lipid classes of similar polarity. These fractions may then be more easily separated by thin-layer chromatography or high performance liquid chromatography for a complete lipid class analysis.