1H nuclear magnetic resonance as a fast tool for determining the composition of acyl chains in acylglycerol mixtures

Several samples containing different proportions of standard compounds such as tristearin, triolein, trilinolein, and trilinolenin, covering a broad range of compositions, some similar to those of edible oils, were prepared by weight. The ¹H nuclear magnetic resonance (NMR) spectra of these samples were recorded and their signals were assigned. It was shown that concentrations of linolenic acyl groups close to 0.4% or higher can be detected by this technique. The area of 5 discrete proton signals of the spectrum was determined. Considering the ratio between this area and the concentration of the corresponding types of hydrogen atoms in the sample, equations calculating the proportions of the acyl groups were deduced. The high level of agreement between data coming from ¹H NMR spectra and data obtained by weight shows the usefulness of this methodology. In addition, it has the advantage that it is very fast and simple in comparison with the classical methods, and does not require a chemical modification of the sample. For this reason, the described method constitutes a valuable alternative for the determination of the proportions of different acyl groups in acylglycerol mixtures, such as, for example, oils and fats.