The discrimination of enantiomers of mandelonitrile by means of 1D 13C NMR and with the aid of the chiral solvating agent (S)-(+)-1-(9-anthryl)-2,2,2-trifluoroethanol (TFAE) is presented. 1H NMR fails for this specific compound because proton signals either overlap with the signals of the chiral solvating agent or do not show separation between the (S)-enantiomer and the (R)-enantiomer. The 13C NMR method is validated by preparing artificial mixtures of the (R)-enantiomer and the racemate, and it is shown that with only 4 mg of mandelonitrile a detection limit of the minor enantiomer of 0.5% is obtained, corresponding to an enantiomeric excess value of 99%. Furthermore, the method shows high linearity, and has a small relative standard deviation of only 0.3% for the minor enantiomer when the relative abundance of this enantiomer is 20%. Therefore, the 13C NMR method is highly suitable for quantitative enantiodiscrimination. It is discussed that 13C NMR is preferred over 1H NMR in many situations, not only in molecules with more than one chiral center, resulting in complex mixtures of many stereoisomers, but also in the case of molecules with overlapping multiplets in the 1H NMR spectrum, and in the case of molecules with many quaternary carbon atoms, and therefore less abundant protons.
Upon storage, crude plant oils will form a solid sediment called gum, which consists mainly of phospholipids (PL). PL are removed during the production of edible oils by a process called degumming. A higher yield is recognized as a major advantage of enzymatic degumming over traditional processes. Robust and accurate PL quantification methods are needed to develop and monitor enzymatic degumming processes. Several techniques, such as atomic emission spectroscopy, liquid chromatography, and thin‐layer chromatography, have been applied for the quantification of PL in edible oils. In the past decade, 31P NMR spectroscopy has been shown to have advantages over these techniques because of the possibility of the simultaneous, fast, and accurate quantification of different PL directly in the oil. This article demonstrates the application of 31P NMR spectroscopy as a method for the quantification of all relevant PL and phosphorous‐containing degradation products in crude and refined oils. In addition, the validation results show that this method is robust because the limit of detection is as low as 5 μmol/100 g oil. Variations of less than 5% were obtained for all P‐containing compounds present in the oils at concentrations above 100 μmol/100 g oil.
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