Isolation of cholesterol oxidation products from animal fat using aminopropyl solid-phase extraction.

Cholesterol oxidation products were separated from triglycerides and cholesterol in a single step on an aminopropyl solid-phase extraction column. The products were purified by subsequent transesterification and saponification, derivatized to trimethylsilyl ethers and analyzed by gas chromatography. Heated cholesterol-containing fat samples were autoxidized by bubbling air through them. When the flow-rate of air was set at 100 ml/min, the concentration of cholesterol oxidation products in the fat increased to a maximum after 1-2 h and then decreased to almost a zero level after 8 h. The concentration of cholesterol oxidation products in the fat increased over a similar time period, without reaching a maximum, when the flow-rate of air was decreased to 5 ml/min.