High-resolution 13C NMR spectroscopy of the carbonyl carbons of triglyceride acyl chains was used as a quantitative method for the regiospecific analysis of the triglyceride fraction of vegetable oils of different botanical origins. The carbonyl carbon resonances of saturated, oleyl and linoleyl chains were baseline resolved. Moreover, the chains attached at the 1,3-position were shifted by 0.4 ppm at higher frequencies than those of the corresponding chains attached at the 2-position. This quantitative NMR method was adopted after demonstrating that proton decoupling affected the carbonyl intensities to the same extent, no significant differences being found among the NOE factors of different acyl chains. The proton-decoupled spectra were measured for quantitative purposes with full NOE enhancement. As a result, the spectrum signal-to-noise ratios were significantly improved in shorter experiment times. The 13C NMR method was used to determine the acyl chain composition of vegetable oil triglycerides, the composition of the two acyl chain pools which entered the glycerol 1,3- and 2-positions and the specificity of each chain for the 2-position.
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Giovanna Vlahov (1998) studied this question.