A quantitative estimation of the behaviour of unsaturated lipid molecular species during their argentation liquid chromatographic separation

Analysis of experimental retention data upon several variants of argentation liquid chromatographic separations of different mixtures of the same lipid class into their molecular species was made to estimate new parameters of their π-complexes for every unsaturated fatty acid residue as its silver ion cluster. Planar reversed-phase liquid chromatography both in the presence and in the absence of silver ions as well as adsorption argentation liquid chromatography were applied for the separation of complex rac-1,2-diacylglycerol samples from three plant sources (cocoa butter, poppy seed, and linseed oils). Every value of the argentation liquid chromatographic separation selectivity for any lipid molecular species upon both planar and column variants of reversed-phase fractionation of different complex samples from native sources into their molecular components is described by additive relative polarity levels of their fatty acid residues. These levels are always connected with equivalent lipophilicity values for every lipid molecule and its chemical potential variations during all variants of reversed-phase liquid chromatography in the presence of silver ion clusters. New parameters for several fatty acid residues of major native polyunsaturated lipid samples may be reflected by different coordination numbers of single silver atoms of its triangular pyramidal nanoclusters. Both hydrophobicity and total polarity levels of the coordination complexes of different lipid molecular species upon their adsorption argentation liquid chromatography may be also quantitatively estimated by their fixed methylene unit variations of these molecular species for two centigrade lipid scales.