Determination of five cholesterol oxidation products in marinated pig feet and hocks by gas chromatography-mass spectrometry

Abstract

An analytical method was developed for the simultaneous determination of five cholesterol oxidation products (COPs) in marinated pig feet and hocks by gas chromatography-mass spectrometry (GC-MS). The five COPs were 7 β -hydroxycholesterol, cholesterol-5 α,6 α -epoxide, 3 β,5 α,6 β -trihydroxycholestane, 25-hydroxycholesterol and 7-ketocholesterol. The sample was extracted with methanol-chloroform (1:2, v/v) and purified by solid phase extraction. Subsequently, the sample was collected for derivatization by N,O-bis(trimethylsilyl)acetamide-trimethyl chlorosilane-1-trimethylsilyllimidazole (3:2:3, v/v/v) (Sylon BTZ). The column temperature was properly programmed, and the selected ion monitoring (SIM) mode was used for the determination of COPs. Under optimum conditions, the five COPs were well separated within 22 min with good separation. The linear range of the five COPs met the requirement of determination, and the average recoveries of the five COPs spiked in the pork samples at three levels were 61.16%-96.96% with relative standard deviations (RSDs) no more than 7.80% (n=3). The limits of detection (LODs) and limits of quantification (LOQs) were in the range of 0.02-47.07 ng/g and 0.06-156.90 ng/g, respectively. This method has a wide line arrange and high sensitivity, and has been successfully applied to the analysis of COPs in actual samples.