Factors Determining the Selectivity of Stationary Phases for Geometric Isomers of Fatty Acids in Gas–Liquid Chromatographic Analysis

Abstract

The chromatographic analysis of food products for trans isomers of monounsaturated fatty acids, which are harmful components, in the presence of an excess of useful cis isomers is considered as a complex problem of considerable current interest. The separation of substances by gas–liquid chromatography occurs in accordance with two mechanisms with different selectivity for geometric isomers based on adsorption on a flat surface, which gives an energy advantage to trans isomers, and distribution in the bulk phase, which leads to the stronger retention of cis isomers. The theoretical model proposed previously to explain the distribution of an adsorbate as its “absorption” by a stationary-phase macromolecule due to a conformational rearrangement in the course of nonspecific interaction was supplemented by polar interactions and hydrogen bonds. The factors influencing the selectivity of a phase for geometric isomers were considered. A theoretical analysis of the experimental data was carried out and the parameters of stationary phases required for increasing the separation selectivity of the trans and cis isomers of fatty acid esters were determined.