Hydrolysis kinetics of phospholipids in thermally stressed intravenous lipid emulsion formulations

A model 20% w/v emulsion, prepared with either a commercially available pharmaceutical grade soy oil or a highly purified grade of oil from the same origin and stabilized with a commercially available mixture of egg yolk phospholipids was passed through a Microfluidics homogenizer until the mean particle size fell below 500 nm diameter. Samples stored in sealed all-glass ampoules were thermally stressed over a temperature range of 5-90 degrees C and samples taken at appropriate intervals for analysis by HPLC. Hydrolysis degradation kinetics were in conformation with the Arrhenius equation. The energy of activation for phosphatidylcholine was virtually identical for emulsions prepared with either pharmaceutical or purified oil (65 and 63 kJ mol-1, respectively). For phosphatidylethanolamine itself the respective activation energies were 53 and 54 kJ mol-1, suggesting that the source of the oil used in preparing the emulsions had no significance in the degradation processes of the resulting systems.