Wednesday, May 28, 2008

Nuclear Magnetic Resonance (NMR)

Nuclear magnetic resonance (NMR) is a technique depending on the basis that nucleus within atoms have spinning properties and this spinning properties is used to determine the absorption and emmission of energy, moreover, this property can be used to determine the electromagnetic properties of nuclei. (Resonance is the vibrational frequency of a moving or rotating object. Magnetic Resonance is a technique, where computer is used for analyzing the response of atoms of hydrogen or any other element to a generated magnetic field. So by this response the electronic images of the atoms or molecular structures of solids can be obtained).

This is used for determining the chemical structure of materials and more properly for organic materials.

Proton NMR (represented by 1H NMR) is the type of NMR spectroscopy in which protons within a molecule or hydrogen atoms are under study for determination of structure. (J Urenjak et al.) It is a non-invasive technique. It has many important uses. (J. D. Otvos et al.) One of the application of 1H NMR is for quantifying plasma lipoproteins.

Carbon NMR is the type of NMR spectroscopy in which carbon atoms are under study for determination of the structure. (L. P. Lindeman et al.) Carbon-13 form is mostly used for this purpose and this is one of the great tools for structure analysis because it is naturally abundant. For molecules with few polar functional groups, like hydrocarbons, the fully proton decoupled carbon-13 NMR spectra are usually much better resolved than the proton NMR spectra.

Zero field NMR (A. Bielecki et al.)has been used when there is no predefined direction in space. In this case, all crystallites contribute equivalently and resolved dipolar splittings can be judged by internuclear distances. The importance of this is in molecular structure determination without the need for single crystals or oriented samples.

References:
A. Bielecki, D. Zax, K. Zilm, and A. Pines, Zero-Field Nuclear Magnetic Resonance. Physical Review letters, 50, Pages 1807 - 1810 (1983).
(Physical Review Letters - 14 March 2008 - American Physical Society Periodical/Physical Review Letters October - December 1980 /Physical Review Letters July-September 20 1965 Bound Volume by American Physical Society )

J. D. Otvos, E.J. Jeyarajah, D.W. Bennett, Quantification of plasma lipoproteins by proton nuclear magnetic resonance spectroscopy. Clinical Chemistry, 1991 Mar;37(3):Pages 377-86.

J Urenjak, SR Williams, DG Gadian and M Noble, Proton nuclear magnetic resonance spectroscopy unambiguously identifies different neural cell types. Journal of Neuroscience, Vol 13, Pages 981-989.

L. P. Lindeman, J. Q. Adams, Chemical Shifts for the Paraffins through C9,
Analytical Chemistry, Volume 43, No. 10, August 1971. Page 1245.


Further Reading:
Nuclear Magnetic Resonance by P. J. Hore

Nuclear Magnetic Resonance Spectroscopy: An Introduction to Principles, Applications, and Experimental Methods by Joseph B. Lambert , Eugene P. Mazzola

Principles of Nuclear Magnetic Resonance in One and Two Dimensions by Richard R. Ernst , Geoffrey Bodenhausen and Alexander Wokaun

Nuclear Magnetic Resonance: Concepts and Methods by Daniel Canet

Encyclopedia of Nuclear Magnetic Resonance by David M. Grant and Robin Harris

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