Determination of cholesterol oxidation products in milk powder and infant formulas by gas chromatography and mass spectrometry.

In this paper a method for the cholesterol oxidation products (oxysterols) determination in milk powder and infant formulas has been presented. In the sample preparation step lipids transesterification has been performed. The recoveries of oxysterols have been determined and ranged from 94.2% to 99.9% for all but 20a-hydroxy cholesterol (74.2%). Detection limits were 0.018-0.034 ppm and the relative standard deviations (RSD) values were 4.6%-18.3%. The method has been utilized for the determination of oxysterols in milk-based infant formulas and milk powder available on the market. The concentration of oxysterols was between 0.04 and 4.20 ppm of a lipid extract fraction.