NMR Spectroscopy Vs. Relaxometry: What's The Difference?

Magnetic resonance (NMR) spectroscopy is the absorption of electromagnetic radiation, typically in the radio wave frequency range, by a nucleus. This causes a change in the molecular ‘spin’ that can be observed for a period of time, for liquid state spectroscopy usually on the order of seconds, over which it relaxes to equilibrium. It's used as an analytical technique and in diagnostic body imaging as well as many other applications including drug discovery.

While both NMR spectroscopy and relaxometry use magnetic resonance properties and involve the same absorption of radio waves, NMR spectroscopy gives chemically specific information about each part of a chemical structure, whereas relaxometry provides information about the bulk properties of a sample being measured.  

What is NMR relaxometry?

Relaxometry refers to the measurement or study of relaxation variables in nuclear magnetic resonance and magnetic resonance imaging. Nuclear magnetic moments in NMR are used to measure specific chemical and physical properties of bulk materials.  This is done via a collection of an FID and either looking at intensity differences at two points or performing an inverse Laplace transform to determine rapid vs. slow relaxation. 

Relaxation of the nuclear spin system is vital for all NMR applications, in both spectroscopy and relaxometry.  The difference is the homogeneity of the field, the data treatment and the amount of information that is contained in the FID. The relaxation rate of the nuclear spin system depends on the mobility of the microscopic environment. 

It also depends on the strength of the applied magnetic field.  Strong magnetic fields cause an increased sensitivity on fast dynamics. But low fields lead to an increased sensitivity on slow dynamics. Because of this, how the relaxation rate functions in relation to the magnetic field strength serves as a fingerprint of the microscopic dynamics.

NMR spectrometers and relaxometers

While relaxometry measurements can be performed on both spectrometers (highly homogenous fields) and relaxometers (low homogeneity fields), typically NMR relaxometers are separate devices that perform relaxation compared to a known suite of samples. This helps to aid data analysis and determine desirable parameters according to the specific applications - solid fat content (SFC) is a common one for example.  This helps to save time and resources in a variety of applications such as food science.

NMR relaxometry is used in food science to determine moisture content, solid fat content, and more. But some benchtop NMR spectrometers such as the NMReady-60PRO can not only perform the fundamental experiments involved in NMR spectroscopy but also those in NMR relaxometry.

NMReady is capable of measuring high-resolution 1D 1H NMR acquisition, which provides invaluable information through speciation, including fatty acid profiles in fish oil or olive oil, for example.  You can also use NMReady to validate product claims.

Looking for benchtop NMR spectrometers for your lab?

Nuclear magnetic resonance is one of the most useful analytical methods in modern chemistry, and now with benchtop NMR spectrometers, you can use NMR spectroscopy in your own lab. To learn more about benchtop NMR spectrometers, NMR spectrometer applications, and NMR interpretation software, contact Nanalysis today.