Fractionation of cis- and trans-oleic, linoleic, and conjugated linoleic fatty acid methyl esters by silver ion high-performance liquid chromatography

Silver ion high-performance liquid chromatography (Ag-HPLC) using two commercially available columns connected in series and a solvent of 0.5% acetonitrile in hexane (1.0 ml/min), was used to fractionate a mixture of conjugated 18:2 isomers (as methyl esters) and resulted in an elution order (10 mu g sample size) of: 9-trans, 11-trans-18:2; 9-cis, 11-trans-18:2. A more complex mixture of cis and trans 9-18:1, 9,11-18:2 and 9,12-18:2 methyl esters could also be fractionated within 25 min. The elution order (10 mu g sample size) was found to be: 9-trans-18:1; 9-trans, 11-trans-18:2; 9-trans, 12-trans-18:2; 9-trans, 11-cis-18:2; 9-cis, 11-trans-18:2; 9-cis-18:1; 9-trans, 12-cis-18:2; 9-cis, 12-trans-18:2; 9-cis, 12-cis-18:2. The Ag-HPLC elution orders differed significantly from those obtained via gas chromatography on a polar stationary phase (30 m SP2380 capillary column; Elution order: 9-trans-18:1; 9-cis-18:1; 9-trans, 12-trans-18:2; 9-cis, 12-trans-18:2; 9-trans, 12-cis-18:2; 9-cis, 12-cis-18:2; 9-cis, 11-trans-18:2; 9-trans, 11-cis-18:2; 9-trans, 11-trans-18:2). The Ag-HPLC system was also used in the semi-preparative separation of a 10 mg sample of 9-trans, 11-trans-18:2 and 9-cis, 11-trans-18:2 fatty acid methyl esters. Published by Elsevier Science B.V.