How Does NMR Spectroscopy Actually Work?

low field nmr spectrometer

Nuclear magnetic resonance (NMR) spectroscopy is a chemistry technique that's used to research and analyze the content and purity of a given sample. For instance, hydrogen is number one most studied nuclei. NMR spectroscopy gives chemists the ability to study hydrogen's molecular structure.

After learning the basic structure of the sample, NMR can be used to determine other physical properties like solubility, diffusion, and phase changes. But how exactly does NMR spectroscopy work?

What's the principle behind NMR?

Every nucleus is electrically charged. When you apply an external magnetic field, energy can be transferred between the base energy and the higher energy level.

This energy transfer occurs at a wavelength corresponding to radio frequencies. This energy is measured and processed to create an NMR spectrum for the specific nucleus being studied.

The resonant frequency of the energy that's being transferred depends on the nucleus' magnetic field. The magnetic field can be affected by electron shielding that depends on the chemical environment.

In fact, it's because the electron shielding depends on the nucleus' chemical environment that information about the chemical environment can be derived from the resonant frequency. A nucleus that's more electronegative will have a higher resonant frequency.

What is spin-spin coupling in NMR?

The magnetic field of the nucleus can be affected by the orientation of other nuclei. This is called spin-spin coupling. Spin-spin coupling can cause each nucleus to split their signal into two or more lines.

How much the signal splits isn't impacted by the nucleus' magnetic field. Because of this, the split is measured as an absolute frequency. Typically, it's measured in Hertz.

The number of splittings determines the number of chemically bonded nuclei surrounding the nucleus being studied. So not only does NMR spectroscopy give chemists the ability to study samples repeatedly without causing harm to the sample, but it also gives chemists the ability to determine characteristics of the surrounding nuclei in the sample.

Looking for a new low field NMR spectrometer?

The first commercial NMR spectrometers were created in the 1950s and quickly became a key tool for research chemists. It's no surprise why. Nuclear magnetic resonance is one of the most useful analytical methods in modern chemistry.

If you're looking for a new low field NMR spectrometer for your lab or classroom, Nanalysis has the NMR spectrometers you need. For more information on our benchtop spectrometers or NMR interpretation software, contact Nanalysis today.