Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: July 29, 2006
Publication Date: January 23, 2007
Citation: Adlof, R.O., List, G.R. 2007. Analysis and characterization of trans isomers by silver-ion HPLC. In: List, G., Kritchevsky, D. and Ratnayake, N., editors. Trans Fats in Foods. Champaign, IL: AOCS Press. p. 195-224. Technical Abstract: Produced by the partial hydrogenation of vegetable oils and present in animal fats and selected seed oils, trans fatty acids [both configurational (cis vs trans) and positional (double bond location may vary from the delta-4 to the delta-16 position on the fatty acid carbon chain) isomers continue to be an integral, if somewhat controversial, part of the fats and oils industry but, due to the large number of trans isomers generated during the hydrogenation process, their isolation and characterization remains difficult. Silver ion chromatography (Ag-HPLC), utilizing columns packed with silver ions bonded to a silica or similar substrate and a variety of different solvent systems [1,2-dichloroethane, dichloromethane, or hydrocarbons (hexane, heptane) with acetonitrile or alcohols (methanol, isopropanol) as polar modifier(s)] has, over the last several decades, proven to be a tremendously powerful technique for the analysis of a wide variety of geometric (cis and trans) and positional (location of olefinic/acetylenic bonds on the fatty acid backbone) fatty acid (FA), fatty acid methyl ester (FAME), mono-/diacylglycerol (MAG/ DAG) and triacylglycerol (TAG) isomers. In this chapter we review the history of Ag-HPLC, retention theories, such recent developments as use of temperature to improve resolution, and the effects of sample size or temperature on current applications (including advantages and limitations of temperature), as well as possible future applications of this powerful methodology to better understand the role of trans fatty acids in human nutrition and metabolism.