NMR Tech Talk: February 2014

The interest in high-resolution bench-top NMR systems is very topical, as institutions consider budgets, TCO, new uses for NMR, versatile deployment options, and a cost-effective new teaching tool. Of course, many of us of a “certain age” will have fond memories of significant research performed on instruments operating at ≤100MHz for 1H. The wave of new systems has great appeal, and stems from advances in permanent magnet designs that use rare earth metals. Interest in this technology runs the spectrum from MRI scanners to the bench-top systems we will discuss today.

Bench-top systems can currently be used for TD-NMR, MRI, and high-resolution NMR. This blog focuses on software concerns high-resolution spectra and issues that come into sharper focus with these systems. Are the existing processing packages and algorithms adequate?

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Traditional high field NMR spectrometers are costly to purchase and maintain, and generally require expert users. NMR provides information about chemical structure, and is a valuable technique in the analytical chemist’s tool kit. Many smaller labs cannot afford such instrumentation, and instead use other techniques to piece together the required information.

An 80MHz bench-top NMR spectrometer has high enough resolution to provide specific structural information about a sample. For example, a mass spectrum of an unknown material provides a molecular mass and possibly a fragmentation pathway, giving structural information. Without further MS information, it is often impossible to be certain of a specific structural isomer, and it is in these cases where a 1H 1D NMR spectrum proves invaluable.

In the case of a possible designer drug sample, for example, it may be crucial to determine whether a functional group is at position 1 (legal) or position 2 (illegal) on an aliphatic chain. Standard mass spectra of both samples will be similar, showing cleavage of similar bonds, but comparison of 1H NMR spectra will be noticeably distinct.