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Abstract
The effect of the mobile phase composition on the retention and resolution of trans positionally isomeric 6-, 9-, and 11–18 : 1 fatty acids was studied on a model mixture by silver ion high performance liquid chromatography (Ag-HPLC). Prior to chromatography, the fatty acids were converted into p-methoxyphenacyl derivatives. Hexane-based and dichloromethane-based mobile phases modified with either acetonitrile or methanol, or isopropanol were examined. The modifiers were found to have a different effect on the resolution, depending on the main solvent component in the mobile phase. In case of hexane being the main mobile phase solvent, best resolution was achieved when using isopropanol as a modifier. In dichloromethane-based mobile phases, best results were achieved with acetonitrile or methanol. The three trans isomers were completely resolved in practically all mobile phases tested, the elution order being 11-, 9-, 6–18 : 1, irrespective of the mobile phase composition.
ACKNOWLEDGMENTS
The partial financial support of the National Scientific Fund, project No X-1009, is gratefully acknowledged. The fatty acid isomers and the Nucleosil column were kindly donated by Prof. B. Herslof from ScotiaLipidTeknik AB, Stockholm, Sweden.