An Improved Silver Ion HPLC Combined with Capillary Gas Chromatography of cis / trans Fatty Acids in Alimentary Fats and
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An Improved Silver Ion HPLC Combined with Capillary Gas Chromatography of cis/trans Fatty Acids in Alimentary Fats and Human Milk Fat Andrzej Stolyhwo & Jarosława Rutkowska
Received: 2 January 2012 / Accepted: 4 June 2012 # The Author(s) 2012. This article is published with open access at Springerlink.com
Abstract A technique of analysis is described using a silver ion-loaded HPLC (Ag+/HPLC) column, gradient elution, and a laser light scattering detector followed by capillary gas chromatography (GC) for the determination of the fatty acid methyl ester (FAME) composition of rapeseed oil, the respective hydrogenated fat, some dietary fats, and human milk fat. With the use of Ag+/HPLC, FAMEs were separated into the following classes: saturated, trans-monounsaturated, cis-monounsaturated, trans–trans-di-unsaturated, trans–cisdi-unsaturated, cis–cis-di-unsaturated, and higher unsaturated FAMEs. Within each class, partial separation of positional isomers was also possible. Fractions of the eluate containing trans and cis C18:1 were separately collected and re-analyzed by GC in order to quantitate the positional isomers eight trans and nine cis in rapeseed oil and in human milk fat. The profiles of eight trans positional isomers in human milk fat and in hydrogenated rapeseed oil were alike but entirely different from that of six C18:1 trans isomers in bovine milk fat. Out of nine C18:1 cis isomers found in hydrogenated fat, only C18:1-9c and C18:1-11c were found in both human and bovine milk fat which may indicate some discrimination which occurs for certain isomers in fatty acid metabolism.
A. Stolyhwo Department of Dietetics, University of Bydgoszcz, Unii Lubelskiej St. 4c, 85-059 Bydgoszcz, Poland J. Rutkowska (*) Department of Instrumental Analysis, Faculty of Human Nutrition and Consumer Sciences, Warsaw University of Life Sciences, Nowoursynowska St. 159c, 02-776 Warsaw, Poland e-mail: [email protected]
Keywords trans fatty acids . Gas chromatography . Silver ion-loaded HPLC . Laser light scattering detector . Cold-pressed rapeseed oil . Hydrogenated fats . Human milk
Introduction The Codex Alimentarius Commission 2004 has adopted a definition proposed by the Danish delegations which is “trans fatty acids are defined as all the geometrical isomers of monounsaturated and polyunsaturated fatty acids (FAs) having nonconjugated (interrupted by at least one methylene group (–CH2–CH2–) carbon–carbon double bonds in the trans configuration”. This includes the trans monoenes (mainly steroisomers of elaidic acid) and the trans isomers of polyunsaturated FAs (e.g., trans dienes, trans trienes etc.) with non-conjugated carbon–carbon double bonds, produced through hydrogenation of oils and fats (both vegetable and animal/marine origin) in the presence of a suitable chemical catalyst. The definition, however, excludes conjugated trans FAs present naturally in animal fats and their products that include conjugated linoleic acid. The US FDA defined trans FA as “unsaturated FAs that contain one or more isolated (i.e.
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