The effect of hydrogen content on estimation of seed oil by pulsed nuclear magnetic resonance

In the nondestructive estimation of seed oil by pulsed nuclear magnetic resonance (NMR), an assumption generally is made that the hydrogen content of the oil in the seed sample under investigation is the same as that of the oil standard or that of the oil in the standard seed samples. The hydrogen content is defined as the number of hydrogen atoms per unit mass of oil. The validity of this assumption has been investigated by; (i) calculating the Hydrogen contents of various oils on the basis, of their reported fatty acid composition, and (ii) experimentally determining the hydrogen contents of cotton and mustard oils obtained from different varieties of seeds. The FID method was used to monitor the NMR signal intensities. Both calculated and experimental values show that that hydrogen contents can be different not only for different oils but also for the same oil extracted from different varieties of the seeds. This variation in hydrogen contents is shown to introduce an error in the oil content values as estimated by NMR methods. The magnitude of this error increases with oil content, and also with the difference in the hydrogen contents.