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United States Department of Agriculture

Agricultural Research Service

Title: Temperature-Enhanced Alumina Hplc Method for the Analysis of Wax Esters, Sterol Esters, and Methyl Esters

item Moreau, Robert
item Kohout, Karen
item Singh, Vijay - UNIV. OF ILLINOIS URBANA

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 10, 2002
Publication Date: December 10, 2002

Interpretive Summary: The major chemical component in all vegetable oils is triacylglycerols, but in recent years the nutritional and "health promoting" value of the other oil components (phytosterols, carotenoids, tocopherols, etc.) has received much attention. Two components in vegetable oils, phytosterol fatty acid esters and wax esters, are very difficult to separate and accurately quantify. In the current study a new method was developed to accurately analyze these two types of molecules. It employs an alumina column and demonstrates that the separation of these compounds is enhanced when the column is heated to 75o. This new method was used to compare several phytosterol-rich food products and evidence was presented to suggest that the method could be used to provide valuable "chemical fingerprints" of each product.

Technical Abstract: Previous attempts at separating nonpolar lipid esters (including wax esters, sterol esters, and methyl esters) have only achieved limited success. Among the several normal phase methods tested, a single recent report of a method employing an alumina column at 30oC, with a binary gradient system, was the most promising. In the current study, modification of the alumna method by increasing the column temperature to 75oC improved the separation of standards of wax esters and sterol esters. Elevated column temperatures also enhanced the separation of fatty acid methyl esters with differing degrees of unsaturation. Evidence was also presented to indicate that the method similarly separated phytosterol esters, based on their levels of unsaturation. With the increased interest in phytosterol- and phytostanol-ester enriched functional foods, this method should provide a valuable way to characterize and compare these products.

Last Modified: 4/21/2015
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