Susceptibility broadening

An equally troublesome and perhaps less common and less appreciated difficulty in the high resolution NMR of these gels is the occurrence of susceptibility broadening.26 Magnetic susceptibility, symbolized by y, occurs... 

The addition of a solid to the solution to analyse induces susceptibility broadening of the NMR proton signals, which can reach several tens of Hz. This effect, in conjunction with shortened Tz relaxation for adsorbed species, may degrade the spectral resolution of aH NMR spectra beyond exploitation. As the latter effect cannot be countered by technological means, only susceptibility-broadening methods will be discussed in this section, but the reader should be aware that exclusively systems in which the solid phase, or any other matrix, does not induce severe relaxation broadening are suitable for chrom-NMR analysis. 

Finally, it is noteworthy that susceptibility-broadening effects are not relevant in declinations of the method in which the retarding agent is soluble, a polymer or a micelle, for instance. 

Stoll ME, Majors TJ, Elimination of magnetic-susceptibility broadening in NMR using magic-angle sample spinning to measure chemical shifts in niobium hydride (NbHx), J. Phys. Rev. B, 24 2859-2862, 1981. 

There is a major subsidiary benefit arising from the application of such large gradients in that strong localized susceptibility-broadening gradients are... 

The major sources of linebroadening such as chemical shift anisotropy, heteronuclear dipolar interaction, first-order quadrupolar interaction as well as magnetic susceptibility broadening, can be almost time-averaged to zero... 

Although these results give insight into the sources of susceptibility broadening, they will not be very relevant for in-flow experiments, because in that situation the infinitely long sample constraint can be easily fulfilled. 

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