SILVER-ION HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC SEPARATION AND IDENTIFICATION OF CONJUGATED LINOLEIC-ACID ISOMERS

This is the first report of the application of silver-ion impregnated high-performance liquid chromatography (Ag+-HPLC) to the separation of complex mixtures of conjugated linolenic acid (CLA) isomers present i n commercial CLA sources and foods and in biological specimens. This m ethod showed a clear separation of CLA isomers into three groups relat ed to their trans,trans, cis,trans or trans,-cis, and cis,cis configur ation of the conjugated double-bond system. In addition, this method s eparated individual positional isomers of the conjugated diene system within each geometrical isomeric group. Following Ag+-HPLC isolation, gas chromatography (GC)-electron impact mass spectrometry, and GC-dire ct deposition-Fourier transformed infrared spectroscopy were used to c onfirm the identity of two major positional isomers in the cis/trans r egion, i.e., Delta 8,10- and Delta 11,13-octadecadienoic acids, which had not been chromatographically resolved previously. Furthermore, the potential of this method was demonstrated by showing different Ag+-HP LC profiles exhibiting patterns of isomeric distributions for biologic al specimens from animals fed a diet containing a commercial CLA prepa ration, as well as for a commercial cheese product.