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Preparative Separation of cis ‐ and trans ‐Isomers of Unsaturated Fatty Acid Methyl Esters Contained in Edible Oils by Reversed‐Phase High‐Performance Liquid Chromatography
Author(s) -
Tsuzuki Wakako,
Ushida Kaori
Publication year - 2009
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/s11745-008-3271-5
Subject(s) - chemistry , high performance liquid chromatography , chromatography , cis–trans isomerism , fatty acid , structural isomer , acetonitrile , fatty acid methyl ester , gas chromatography , organic chemistry , biodiesel , catalysis
In order to measure exactly the trans ‐fatty acids content in food materials, a preparative group separation of cis ‐ and trans ‐isomers of unsaturated fatty acid methyl esters (FAMEs) was achieved by an isocratic reversed‐phase HPLC (RP‐HPLC) method. The trans ‐isomers of 16:1, 18:1, 18:2, 18:3, 20:1 and 22:1 FAMEs were readily separated from the corresponding cis ‐isomers by a COSMOSIL Cholester C18 column (4.6 mm I.D. × 250 mm, Nacalai Tesque) or a TSKgel ODS‐100Z column (4.6 mm I.D. × 250 mm, TOSOH), using acetonitrile as the mobile phase. This method was applied for determining the trans ‐18:1 fatty acid content in partially hydrogenated rapeseed oil. The methyl esters of cis ‐ and trans ‐18:1 isomers of the oil were collected as two separate fractions by the developed RP‐HPLC method. Each fraction was analyzed by gas chromatography (GC) for both qualitative and quantitative information on its positional isomers. By a combination of RP‐HPLC and GC methods, a nearly complete separation of cis ‐ and trans ‐18:1 positional isomers was achieved and the trans ‐18:1 fatty acid content was able to be evaluated more precisely than is possible by the direct GC method. The reproducibility of cis ‐ and trans ‐18:1 isomers fractionated by the RP‐HPLC method was better than 98%. These results suggested that the preparative RP‐HPLC method developed in this study could be a powerful tool for trans ‐fatty acid analysis in edible oils and food products as an alternative to silver‐ion chromatography.