Comparison of Solid-Phase Extraction Methods for the Cleanup of Cholesterol Oxidation Products

Cholesterol oxidation products (COPs) may accumulate in foods of animal origin during processing or storage. As they represent a potential health risk, a need exists for rapid and efficient methods to monitor the occurrence of COPs in the human diet. Methods involving saponification to remove triacylglycerols suffer from artifact formation; therefore, alternatives involving solid-phase extraction (SPE) cartridges have been proposed. The efficiencies of several SPE methods for the cleanup of COPs were compared, and a combination of a silica cartridge followed by an NH 2 cartridge was found to be optimal for the removal of matrix components. COPs added at the 150 ppb level to milk fat were recovered by the method proposed ≥90% except cholestanetriol, for which the recovery rate was only 52%. Separation and quantification of COPs were done by GC/MS in full-scan mode. Splitless injection of COPs at a concentration of 0.3 ng/μL produced signal-to-noise ratios between 1:10 and 1:200 for epoxycholesterol and 7β-hydroxycholesterol, respectively.