NMR provides a truly unique way to probe samples. While most forms of instrumentation probe the chemical, optical or electronic structure of molecules and atoms, NMR keys off the magnetic properties of atomic nuclei, which are ultimately due to the quantum mechanical–spin magnetic moment of the component neutrons and protons in each nucleus.
In NMR, the sample is placed in a magnetic field that causes all the magnetic moments of the atomic nuclei to align. Radio frequency (RF) electromagnetic radiation of certain frequencies can cause particular nuclei to flip into a higher energy state in which the nuclear magnetic moment is opposite the magnetic field. A simple form of NMR is to remove the RF field and allow the nuclei to “relax” back into their lower-energy states, which produces a signal that can be measured. Relaxometry or time-domain NMR provides information on sample composition but is generally not as powerful as NMR spectroscopy, which provides more information on the complete frequency dependence of the sample response.
The power and resolution of NMR is strongly tied to the strength of the magnetic field. While research NMR has pushed ever further toward stronger magnets, there is also a significant market for low-field NMR instruments that fit on a benchtop.
High-field magnets depend on powerful superconducting electromagnets, but benchtop NMR is much more likely to use a permanent magnet. Rare-earth magnets can provide significant field strengths at relatively modest weights. Powerful NMR systems can be used to probe the molecular structure of complex proteins, but benchtop systems are more limited. Nevertheless, there are many important applications for benchtop NMR.
The most common application is food analysis, for which NMR can be used to measure water and fat content. The next most-common applications involve the behavior of polymers, elastomers and paints. Other applications include reaction monitoring, petrochemical and geological measurements, moisture and density measurements in various materials, basic research and educational use.
The total market, including aftermarket and service, for benchtop NMR was roughly $100 million in 2014. Oxford Instruments and Bruker are the two leading companies, offering both benchtop relaxometry NMR and NMR spectrometers. New Zealand–based Magritek has commercialized technologies developed from academia. Most of the other market participants are relatively specialized companies, with the obvious exception of Thermo Fisher Scientific, which entered the market with the acquisition of picoSpin (see IBO 12/31/12). Nanalysis is another significant vendor. Other vendors include Resonance Systems (marketed by Process NMR Associates), Stelar, ACT and Niumag, a Chinese company. Several of these vendors also offer benchtop MRI systems, suitable for small-animal imaging or materials analysis.
g number of regulations worldwide.
Benchtop NMR at a Glance:
• Oxford Instruments
• Food and Beverage