Phospholipids in Soybean Lecithin
Lecithin is a food supplement from either soybeans or corn, It is a mixture of phospholipids, represented above. (The fatty acids will vary.) R can be choline, hydrogen (acid), inositol, ethanolamine and some other substituents. The client wishes to know the level of the four major components in his products. After weighing the sample and the primary standard, viz., triphenyl phosphate, and a sample preparation to remove interferences for paramagnet ions, we use 31P NMR to quantify the four or more components, cf. Meneses, Glonek.
Meneses, Glonek, Journal of Lipid Research, 29, (1988) p679
We use triphenyl phosphate as our chemical shift reference (-17.9ppm) as well as our primary standard. The 31P shifts are the following: phosphatidylcholine -0.84ppm, 'inisito l -0.41ppm, 'ethanolamine -0.05ppm, phosphatitic acid +0.46ppm. The signals from these are integrated against that of triphenyl phosphate. Knowing the weights of sample and standard, we can calculate the percentage of each. Typical values are 14%, 5%, 10%, 2% respectively.