Will Compact Benchtop NMR Work For Me?

By Nanalysis Corp.

Most chemists are familiar with high-field superconducting magnets (usually 400MHz+). The benchtop NMR is high-resolution, meaning that the field is homogenous enough to observe discrete peaks and multiplicities, but it is low-field permanent magnet (≤100 MHz). These instruments were not meant to replace high-field NMR, certainly not, but rather to provide an affordable, accessible and automatable alternative to the more traditional instrumentation. This allows NMR Spectroscopy to be introduced into applications that were previously underserved or even ignored. There are two main trade-offs to be made as one moves to low-field NMR. The first is sensitivity. A spectrometer's sensitivity is directly correlated to its field strength, and the resultant Boltzmann distribution of nuclear spins. This means that lower-field spectrometers are inherently less sensitive and will have a lower signal-to-noise ratio (SNR) than high-field counterparts. To offset this fundamental constraint there are two options: (i) increase the concentration of the sample (ii) increase the number of scans acquired for each sample The second limitation is resolution, or more accurately dispersion (Hz/ppm). As the spectral width (in Hz) decreases with field, at lower fields peaks tend to be closer together or exhibit more second order effects. An example of peak separation is the resolution of the CH group of ibuprofen in 100 MHz, whereas there is slight overlap in 60 MHz. There are a number of software tools to assist analysis of such spectra, please inquire for more details. If you are unsure as to whether or not your application is amenable to the Nanalysis Benchtop NMR Spectrometers, please don't hesitate to contact us for more information.