DIFFUSE-REFLECTANCE FOURIER-TRANSFORM INFRARED-SPECTROSCOPY OF VEGETABLE OIL TRIGLYCERIDE ADSORPTION ON SILICIC-ACID

The adsorption of triglyceride by silicic acid from hexane miscellas was observed with diffuse-reflectance Fourier transform infrared spectroscopy. Triglyceride was adsorbed by hydrogen bonding to silanol groups through the ester carbonyl group. Addition of isopropanol (IPA) to the triglyceride-hexane solution prior to adsorption resulted in unchanged triglyceride adsorption on silicic acid despite IPA's ability to adsorb on silicic acid and hydrogen-bond with triglyderide. Washing the triglyceride, adsorbed on silicic acid, with hexane containing IPA resulted in partial desorption of the triglyceride and a small amount of IPA being adsorbed. Triglyceride desorption into fresh hexane-IPA is due to the establishment of a new equilibrium of lipid and IPA between hexane and silicic acid. The relative strengths of all the possible pairwise interactions among triglyceride, IPA and silicic acid are revealed by the relative amounts of adsorption under various conditions.