Principles of NMR Spectroscopy

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. 

Figure 12.2. OvQview of the principles of NMR spectroscopy. Polarization of nuclear spins by a magnetic field is perturbed by plication of a radiofiequency (rt) pulse. The resultant signal is Fourier transformed, to yield a spectrum reflecting the numbCT and environments of nuclei in the sample.

Now that the principles of NMR spectroscopy have been introduced, we will see how NMR spectra of the two most common nuclei—hydrogen and carbon-13—are obtained. The principles described for carbon-13 are applicable to many other spin- /2 nuclei, such as nitrogen-15, fluorine-19, silicon-29, and phosphorus-31. Topics to be discussed include the components of a typical NMR spectrometer, preparation of a sample, signal optimization techniques, spectral acquisition, selection of processing parameters, spectral presentation, and calibration of the spectrometer. 

The principle of NMR spectroscopy is based on the magnetic properties of the nuclei of certain atoms. Atoms that contain odd number(s) of protons or neutrons behave like a magnet and possess a spin. Thus, atoms of hydrogen... 

The Reader It is assumed that the reader understands the fundamental principles of pulse Fourier transform spectroscopy (PFT) and is proficient in using the MS-Windows operating system and Windows based programs. The references at the end of section 1.4 list both introductory and comprehensive texts on the main principles of NMR spectroscopy. Furthermore the reader should be familiar with computer environments, as working on a spectrometer inevitable requires computer management skills. 

In this chapter NMR-SIM is used to illustrate the theoretical principles of NMR spectroscopy instead of the more usual pure mathematical description. There are many textbooks, reviews and original papers in the literature dealing with the fundamentals of NMR spectroscopy and the reader is referred to them [2.1 - 2.7]. Alternatively the reader can use the list of references at the end of chapter 5 but these relate primarily to the pulse sequences discussed in that chapter. The design of any new experiment always starts with a formal analysis of the problem and an examination of the coherence transfer processes necessary to obtained the required information. The present chapter focuses on three items ... 

This chapter reviews the use of P NMR spectroscopy for soil, water and other environmental samples. After a brief overview of the principles of NMR spectroscopy, the requirements for a successful NMR experiment are described. Finally, literature on P NMR spectroscopy in soils and environmental samples is reviewed, followed by suggestions for future research needs. 

This section provides a short summary of the principles of NMR spectroscopy. More detailed descriptions are available in textbooks (e.g. Wilson, 1987 Canet, 1996) and review articles (e.g. Wilson, 1991 Preston, 1993,1996, 2001 Knicker and Nanny, 1997 Randall etal., 1997 Veeman, 1997 Lens and Hemminga, 1998). 

This article provides a description of the basic principles of NMR spectroscopy. The many applications of this technique, which make it indispensable as a tool for the analytical chemist, are described in subsequent articles, which also include discussion of advanced techniques such as the NMR of solids, multidimensional NMR, and MRI. 

Polypropylene has been studied in great detail, and the stereotactic composition and sequence have been measured by NMR spectroscopy. The following section presents the essential principles of NMR spectroscopy needed to understand the interpretation of the spectra of polypropylene. The technical details are based on the book Chain Structure and Conformation of Macromolecules ... 

The principles of NMR spectroscopy are the same as those for NMR spectroscopy. When placed in an external magnetic field, nuclei adopt one of two spin states, whose energy difference is determined by the strength of the field (Fig. 8.19). Exposing such nuclei to electromagnetic radiation that has the appropriate energy produces the resonance condition (Eq. 8.7). This means that the spin flip associated with transition from one energy level to another (Fig. 8.20) may occur. 

Basic Principles of nmr-Spectroscopy of Oriented Molecules The Spin Hamiltonian... 

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