Acetylation of Soybean Lecithin and Identification of Components for Solubility in Supercritical Carbon Dioxide

There is a growing interest to develop environmentally friendly surfactants for utilization with supercritical carbon dioxide (scCO₂), which is a “green” solvent with many industrial applications. The goal of the present work was to separate the commonly used soybean lecithin into a phospholipid-rich fraction, acetylate this fraction, and then test its solubility in scCO₂ to gauge its suitability as a surfactant for potential scCO₂-based applications. Soybean lecithin was first purified by fractionation using acetone and ethanol and then acetylated with acetic anhydride. The acetylated lecithin was further purified by fractionation with acetone to separate the acetylated fraction from the nonacetylated fraction. High-performance liquid chromatography and electrospray ionization mass spectrometry were utilized to characterize these fractions. The various acetylated phospholipid fractions were then tested for solubility in scCO₂ under various pressures and temperatures using both a cloud-point and a Fourier transform infrared apparatus. Acetylation was found to increase the solubility of the phospholipids in scCO₂, and N-acetylated phosphatidylethanolamine (NAc-PE) was found to be the most soluble component of the acetylated phospholipids. Keywords: Acetylation; carbon dioxide; lecithin; phase equilibria; phospholipids