Principles of NMR

The first successful detection of NMR in condensed matter was achieved independently in 1945 by the groups of Felix Bloch [Biol] and Edward Purcell [Purl]. With the discovery of the chemical shift in 1951, that is the fine structure of the resonance line depending on the electronic environment of the nuclei, NMR was rapidly becoming a tool for chemical analysis of molecules dissolved in liquids [Ami]. In solids this fine stmcture is not as 

The next milestone, in the history of NMR [Frel], was the extension of the NMR spectrum to more than one frequency coordinate. It is called multi-dimensional spectroscopy and is a form of nonlinear spectroscopy. The technique was introduced by Jean Jeener in 1971 [Jeel] with two-dimensional (2D) NMR. It was subsequently explored systematically by the research group of Richard Ernst [Em 1 ] who also introduced Fourier imaging [Kuml]. Today such techniques are valuable tools, for instance, in the structure elucidation of biological macromolecules in solution in competition with X-ray analysis of crystallized molecules as well as in solid state NMR of polymers (cf. Fig. 3.2.7) [Sch2]. 

The use of NMR for imaging was demonstrated in 1973 by Paul Lauterbur for medical applications [Lau 1 ] and by Peter Mansfield [Man 1 ] for materials. Before that the potential of NMR for medical diagnostics had already been recognized by Raymond Damadian in 1971 [Daml]. 

In the NMR measurements, samples are placed in a strong magnetic field and irradiated with radiofrequency radiation. The spin state of a nucleus splits corresponding to the spin number /, which is called Zeeman splitting. For the nuclei of / = 1 /2, H, C, N, and so on, which are popular in polymer analysis, the spin state splits into two energy states. The energy difference is expressed by 

Polymer Morphology Principles, Characterization, and Processing, First Edition. Edited by Qipeng Guo. 2016 John Wiley Sons, Inc. Published 2016 by John Wiley Sons, Inc. 

Because the magnitude of y depends on the nucleus, the resonance frequency of v is characteristic of the nucleus, which enables the independent measurement of constituent elements such as and 

From NMR measurements, a lot of parameters can be obtained. Recent development of the hardware and the pulse sequences enables us to measure structural parameters such as the bond length, the dihedral angles, and so on, directly [3], However, the measurements sometimes require isotopic labeling and long measuring time. NMR chemical shift and the relaxation times are suitable for the practical analysis of polymer morphology. 

NMR chemical shift is the peak position and corresponds to the resonance frequency of the nuclei. Even for the same nucleus, the electronic environment is dependent on the chemical structure and the functional groups, which is reflected in the resonance frequency. In other words, the chemical shift is affected by the structural changes and is the measure for the conformation and the crystal structures [4]. 

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P. T. Callaghan 1991, Principles of NMR Microscopy, Clarendon Press, Oxford. 

The principle of NMR can be explained in quantum mechanical terms. The angular momentum of a spinning nucleus, quantized both in magnitude and direction, is given by the equation... 

The underlying physical principles of NMR have been established and are well understood.8 Applications of both solid- and solution-state NMR spectroscopy can be found in many different disciplines. It is routinely used in structural elucidation of organic and inorganic compounds, polymers, and biomolecules (e.g., proteins, nucleic acids, and carbohydrates). Additionally, NMR can be used to study molecular interactions (e.g., protein-protein and protein-ligand), molecular dynamics, and chemical reactions. It has also been used extensively in medical research and imaging (magnetic resonance imaging). 

Electromagnetic Techniques Sensors based on the related principles of NMR and NQR have been successfully developed. These are active techniques that excite the electromagnetic interactions between the atomic nuclei... 

There are excellent textbooks available on the principle of NMR for a variety of readers, ranging from the readers who may have relatively little background in physical sciences [4,5, 6] to NMR specialists [7,8]. A brief outline on selected aspects of the principle of NMR is given in this section. 

This equation depicts a basic principle of NMR and the experimentally observed quantity. 

Before describing the application of Nuclear magnetic resonance (NMR) spectroscopy to potentized homeopathic drugs we would first discuss the basic principles of NMR spectroscopy. This spectroscopy is a powerful tool providing structural information about molecules. Like UV-visible and infra red spectrometry, NMR spectrometry is also a form of absorption spectrometry. Nuclei of some isotopes possess a mechanical spin and the total angular momentum depends on the nuclear spin, or spin number 1. The numerical value of I is related to the mass number and the atomic number and may be 0, Vi, 1 etc. The medium of homeopathic... 

The aim of this text is to introduce the fascinating topic of the hyphenation of chromatographic separation techniques with nuclear magnetic resonance spectroscopy to an interested readership with a background either in organic, pharmaceutical or medical chemistry. The basic principles of NMR spectroscopy, as well as those of separation science, should previously be known to the reader. 

The measurement of SFC by pNMR is commonly used to monitor fat crystallization. It is, however, generally less sensitive than absorbance spectrophotometry (see below) in the early stages of crystallization, as crystals can be visible before solid fat is detectable by pNMR (Wright et al., 2001a). Notwithstanding this, Wright et al. (2000) found a strong correlation between the induction time measured by pNMR and that measured by absorbance spectrophotometry for three milk fat systems. The principles of NMR are described in Chapter 20. 

NMR is incredibly versatile it can even scan living human brains (see picture) but the principle is still the same being able to detect nuclei (and hence atoms) in different environments. We need first to spend some time explaining the principles of NMR. 

Because NMR imaging constitutes a very broad area from human studies to animals, microscopy, and solids, there are many specialized books in the field. We mention two that include good discussions of many aspects of the techniques NMR in Physiology and Biomedicine edited by Robert Gillies134 and Principles of NMR Microscopy by Paul Callaghan.135 About 20% of the articles in the Encyclopedia of NMR relate to NMR imaging and to in vivo spectroscopy. All aspects of the technology, as well as many applications to biomedicine and to studies of solid materials, are included. 

Principles of NMR and the importance of this biomolecular analytical technique... 

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