Adsorption of soy oil phospholipids on silica

An experimental method for adsorption of phospholipids from soybean oil was developed based on chromatographic properties of the oil components. The traditional method for removing phospholipids involves hydrating the gums. However, when crude oil in hexane is applied to thin layers or columns of silica, the phospholipids irreversibly adsorb. The triglycerides can be eluted with non‐polar solvents and phospholipids with a polar solvent system. Hence, there is a basis for a selective adsorption of phospholipids on silica. The system involved stirring one hundred milliliters of oil in solvent (i.e., miscella) with one gram of silica for 15 min. The phosphorus content, before and after the reaction, was analyzed by wet ashing and Fiske‐Subbarow colorimetric reaction. Addition of isopropanol (at least 1%) to the hexane miscella caused an increase in phosphorus adsorption, most likely due to liberating triglyceride from adsorption sites. Increased adsorption was achieved by deactivating the silica. Oil concentration did not appear to affect the adsorption. The amount of phosphorus adsorbed depended on the concentration of the phospholipid. When phospholipid adsorbed per gram of silica is plotted vs the residual phospholipid, the plot resembles a Freundlich isotherm for reversible adsorption. Yet the adsorption is irreversible. Possible explanations for this type of adsorptive behavior are explored.