Determination of hydroperoxides in liposomes by the modified IDF and the modified tiron methods

Two new methods, the modified International Dairy Federation and the modified Tiron methods, were developed for the determination of hydroperoxides in liposomes. Interferences of alpha-tocoferol and egg-phosphatidylcholine (EPC) required a solid-phase extraction before the analysis to eliminate alpha-tocoferol and a fluid-fluid extraction based on the solvent triangle of Bligh and Dyer to separate EPC. The developed color, using thiocyanate and Tiron, respectively, as complex-formers for the generated ferri-ions, was measured spectrophotometrically. Both techniques showed good reproducibility and high sensitivity. Peroxide contents of 0.04 and 0.07% (g/g) in EPC samples were easily determined.