High Performance Reverse Phase Chromatography of Triglycerides, Cholesterol and Cholesteryl Esters and Its Application in the Analysis of Natural and Oxidized Oils

[摘要] Methods have been developed for the separation of triglycerides, cholesteryl and heated olive oil methyl esters using high performance reverse phase chromatography (HPRC). Preliminary studies on the separation of triglycerides showed the effect of packing characteristics (particle size bonded alkyl chain length, etc.) and the mobile phase composition and properties. The results indicate that better separation was achieved on a packing with an octadecyl hydrocarbon stationary phase bonded to a 5 (mu) silica gel particle than those accomplished on a shorter alkyl chain bonded to a larger particle silica gel. The optimum mobile phase was found to differ according to the packing used.Resolution of critical pairs was accomplished on an octadecyl alkyl chain bonded column. Elution of these critical pairs was found to correlate with their molecular weight and shape and their degree of unsaturation. The elution sequence of molecules with the same Equivalent Carbon Number (ECN) starts with those with the highest number of double bonds and terminates with those with the lowest number of double bonds, with the lower ECN molecules eluting ahead of those with the higher ECN, and with cis isomers eluting ahead of their trans partners.Complete separation of cyclic monomer esters, which are known to be toxic substances in heated fats, has been achieved using this system where no other single system was capable of such a separation.This system of analysis was applied in the separation of the triglycerides of olive, soybean, palm and corn oils, lipoprotein and liver lipid cholesterol and cholesteryl esters; and the separation of thermally oxidized olive oil, methyl esters and the detection for the presence of cyclic monomer esters in these oils. Fractions of these esters were collected and subsequently analyzed by gas chromatography-mass spectrometry for their structure determination.

[关键词] Agriculture, Food Science and Technology