The effect of instrument resolution on diffusion coefficients measured using NMR spectroscopy

This study presents a numerical simulation of the performance of an NMR spectrometer in which the influence of equipment with both low and high spatial resolutions is investigated. The results indicate that a low resolution NMR with a wide sensitivity curve may be unable to provide an accurate estimation of the moisture profile along the whole length of a test sample where the moisture gradient changes abruptly. It cannot provide accurate moisture information over a distance measured from each end of the test sample equivalent to the effective width of the sensitivity curve. However, a low-resolution spectrometer does not show any significant errors when calculating liquid diffusion coefficients, although the range of moisture contents over which they can be measured is limited. This study suggests that to avoid errors and practical difficulties, NMR spectrometers for moisture measurement should be selected carefully by matching the effective width of the sensitivity curve to the moisture properties of the material to be measured.