COMPLETE SEPARATION OF THE GEOMETRICAL-ISOMERS OF LINOLENIC ACID BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH A SILVER ION COLUMN

A method has been developed for separation of linolenic acid and its s even isomers by HPLC on a silver-ion-loaded column. The standard 18:3 isomers, isolated from a heated linseed oil or prepared by isomerizati on of linolenic acid, were converted into phenacyl esters and detected by UV at 238 nm. The use of low temperature (10-degrees-C) combined w ith a gradient of dichloromethane and methanol enabled separation of a ll the cis/trans isomers. The peaks were identified by comparison of E CL values with those of a standard mixture, by chromatographing collec ted HPLC fractions on a polar GC column. HPLC quantification was compa red with GC analysis. There was satisfactory agreement between the two methods. This method could be used for separation, collection and qua ntification of 18:3 fatty acids with trans double bonds in different o ils and foods.