Quantitative Determination of Fatty Acid Compositions in Edible Oils Using J-Selective 13C QDEPT

We propose a J -selective quantitative distortionless enhancement by polarization transfer ( J -selective QDEPT) 13 C NMR method with enhanced sensitivity for accurate determination of the fatty acid compositions of edible oils. The J -selective QDEPT protocol is developed by targeted optimization of the known Q-DEPT + experiment. Based on the one-bond C-H J -coupling constants ( 1 J CH ) which can be measured with the heteronuclear two-dimensional J -resolved 13 C NMR spectrum, it is possible to optimize the polarization transfer delay Δ and the reading pulse angle ⊖ , thus enabling the QDEPT experiment further enhancing 13 C resonance signals which have narrow 1 J CH ranges over the traditional untargeted Q-DEPT. For edible oil applications, it is demonstrated that this procedure brings a 2.2 enhancement factor against 1.3 of the traditional untargeted Q-DEPT compared to the standard inverse-gated 13 C experiment, even with a shorter relaxation delay for the two QDEPT experiments. Another advantage of J -selective QDEPT is that a smaller number of quantitative scans are needed to reach a uniform enhancement for different CH n ( n  = 1, 2, 3) groups. These features of the J -selective QDEPT are particularly attractive for batch analysis in the food industry.