Concentration dependence of13C NMR spectra of triglycerides: implications for the NMR analysis of olive oils

A systematic investigation of the concentration dependence of the 13C NMR spectra of pure triglycerides from olive oils was performed. It was found that (i) the chemical shift of each carbon of a given fatty acid is independent of the nature of the other two fatty acids in the triglyceride; (ii) in each fatty acid residue the chemical shifts of some carbons depend on the acyl positional distribution in the triglyceride; and (iii) the chemical shifts show a marked concentration dependence. These properties are ascribed to the lack of any specific intramolecular interactions. They are analytically favorable, as they allow the tabulation of chemical shifts as a function of concentration for any fatty acid in any position, regardless of the composition of the triglyceride to which they belong. These shifts may therefore be used for the systematic characterization of edible oils.