NMR stands for Nuclear Magnetic Resonance. Though it sounds "nuclear", it is neither radiao active nor chemically hazardous (the magnetic field may most likely pose dangers to some individuals, however). It is very similar to UV or IR, in that
it basically involves transitions between nuclear spin states while UV relates to transitions between electronic states and
IR relates to transitions between vibration/rotational states. Thus it is a spectroscopy. In most cases, the energy difference between most spin states is very small, resulting in NMR being
a less sensitive method and of lower frequency. The useful frequency range of NMR is typically from tens of mega-Hertz or hundreds of mega-Hertz.
The properties observed in NMR include chemical shifts, scalar coupling (or bond correlation), dipolar coupling (nuclear Overhauser effect),
residual dipolar coupling and relaxations. Of course, peak intensities (or integrals) can be used for quantitative analysis.
First, NMR is one of the most powerful structural tools. Chemical shift reflects a given nucleus' chemical environment; scalar coupling reveals bond connections
between nuclei; NOE (nuclear Overhauser effect) frequently results from short distance (within 5A) between nuclei; relaxations correlate to the molecular overall tumbling as well as local interactions.
Second, NMR is also a analytical tool. NMR signal is proportional to the number of observed nuclei under a given set of conditions.
It does not require the presence of any chromophore, and there is no need to calibrate with the same known compound.
Third, because of the high resolution of NMR, it is possible to identify multiple components in a mixture, without real phsysical separations.
Thus it offers a as-it-is analysis for a sample.
|What's special about NMR?
Other than the personal belief that NMR is one of the most powerful and versatile research tools, I think NMR is also an excellent example
of quantum physics. Not only you can analyse the process or predict the outcome of a NMR experiment, but also you can easily manipulates spin states
so that only desired results are produced.
|Where is NMR used?
NMR has been most frequently used in structural determinations for both bio and organic molecules. At Purdue, NMR has been used in metabolomics and protein dynamics.
Contact me if you think NMR might be of any help for your problem.
|What is the requirement for NMR?
First, the observed compound is desired to be dissolved in a solution
Second, the amount of compound is preferred to be in micro-molar or higher concentration, with a volume of 300 ul or higher.
Last updated: March, 2009