Seed oil determination without weighing and drying the seeds by combined free induction decay and spin‐echo nuclear magnetic resonance signals

Abstract

AbstractThe free induction decay (FID) and echo signals in a spin‐echo pulse sequence have been used for seed oil determination without weighing and drying the seeds with nuclear magnetic resonance (NMR) equipment that has a magnetic field of low homogeneity. Earlier known methods, based on use of the FID signal to determine seed oil, become inapplicable when the magnetic field homogeneity is poor, because the angular position of seed significantly affects the signal. The present method, which elegantly eliminates the angular dependence, involves sampling the FID signal at 10 µs after a 90° pulse and the subsequent echo signal at 100 µs formed by applying a 180° pulse at 50 µs. Such short pulse spacing in spin‐echo sequence produces almost a full oil signal. It also eliminates the effects of sample‐to‐sample variation inT2 and molecular diffusion on oil signal. The oil values obtained by this method are in good agreement (correlation for mustard: 0.952; linseed: 0.99; and for peanut: 0.912) with the values obtained by the well established and accurate pulsed NMR method, which is based on the measurement of the FID signal of oil in dried and weighed seeds.