Nuclear magnetic resonance spectroscopy combined

NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY COMBINED WITH ULTRASOUND... 

NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY COMBINED WITH ULTRASOUND John Homer, Larysa Paniwnyk, and... 

Marx A, de Graaf AA, Wiechert W, EggeUng L, Sahm H. Determination of the fluxes in the central metabolism of Corynebacterium glutamicum by nuclear magnetic resonance spectroscopy combined with metabolite balancing. Biotechnol Bioeng 1996 49 111-29. 

Spraul, M., Hofmann, M., Ackermann, M., Nicholls, A. W., Damment, S. J. P., Haselden, N. J., Shockcor, J. P., Nicholson, J. K., and Lindon, J. C. (1997) Flow injection proton nuclear magnetic resonance spectroscopy combined with pattern recognition methods Implications for rapid structural studies and high throughput biochemical screening. Anal. Commun. 34, 339-341. 

Homer J, Paniwnyk L and Palfreyman SA (1996) Nuclear Magnetic Resonance Spectroscopy Combined with Ultrasound. Advances in Sonochemistry 4 75-99. 

Nuclear Magnetic Resonance Spectroscopy. Bmker s database, designed for use with its spectrophotometers, contains 20,000 C-nmr and H-nmr, as weU as a combined nmr-ms database (66). Sadder Laboratories markets a PC-based system that can search its coUection of 30,000 C-nmr spectra by substmcture as weU as by peak assignments and by fiiU spectmm (64). Other databases include one by Varian and a CD-ROM system containing polymer spectra produced by Tsukuba University, Japan. CSEARCH, a system developed at the University of Vieima by Robien, searches a database of almost 16,000 C-nmr. Molecular Design Limited (MDL) has adapted the Robien database to be searched in the MACCS and ISIS graphical display and search environment (63). Projects are under way to link the MDL system with the Sadder Hbrary and its unique search capabiHties. 

When simple Hquids like naphtha are cracked, it may be possible to determine the feed components by gas chromatography combined with mass spectrometry (gc/ms) (30). However, when gas oil is cracked, complete analysis of the feed may not be possible. Therefore, some simple definitions are used to characterize the feed. When available, paraffins, olefins, naphthenes, and aromatics (PONA) content serves as a key property. When PONA is not available, the Bureau of Mines Correlation Index (BMCI) is used. Other properties like specific gravity, ASTM distillation, viscosity, refractive index. Conradson Carbon, and Bromine Number are also used to characterize the feed. In recent years even nuclear magnetic resonance spectroscopy has been... 

In the case of heterogeneous polymers the experimental methods need to be refined. In order to analyze those polymers it is necessary to determine a set of functions / (M), which describe the distribution for each kind of heterogeneity i This could be the mass distributions of the blocks in a diblock copolymer. The standard SEC methods fail here and one needs to refine the method, e.g., by performing liquid chromatography at the critical point of adsorption [59] or combine SEC with methods, which are, for instance, sensitive to the chemical structure, e.g., high-pressure liquid chromatography (HPLC), infrared (IR), or nuclear magnetic resonance spectroscopy (NMR) [57],... 

Non-specific sum parameter analysis [12,13], which is still used today, failed [14,15] in the analyses of some of these compounds. Chromatographic methods in combination with non-substance specific detectors, e.g. colorimetric and photometric [5] or with substance specific detectors such as IR (infrared spectroscopy), NMR (nuclear magnetic resonance spectroscopy) or MS (mass spectrometry), are applied increasingly nowadays. 

Hyphenated analytical techniques such as LC-MS, which combines liquid chromatography and mass spectrometry, are well-developed laboratory tools that are widely used in the pharmaceutical industry. Eor some compounds, mass spectrometry alone is insufficient for complete structural elucidation of unknown compounds nuclear magnetic resonance spectroscopy (NMR) can help elucidate the structure of these compounds (see Chapter 20). Traditionally, NMR experiments are performed on more or less pure samples, in which the signals of a single component dominate. Therefore, the structural analysis of individual components of complex mixtures is normally time-consuming and less cost-effective. The... 

Nuclear magnetic resonance spectroscopy is an established technique for studies of stereoselective intermolecular interactions. The application of this technique in combination with CE has been discussed in several review papers (3,4,62,63). In this overview, the potential of NMR spectroscopy is illustrated using just a few examples from the authors own studies. The... 

The hyphenation of capillary electromigration techniques to spectroscopic techniques which, besides the identification, allow the elucidation of the chemical structure of the separated analytes, such as mass spectrometry (MS) and nuclear magnetic resonance spectroscopy (NMR) has been widely pursued in recent years. Such approaches, combining the separation efficiency of capillary electromigration techniques and the information-rich detection capability of either MS or NMR, are emerging as essential diagnostic tools for the analysis of both low molecular weight and macromolecular compounds. 

The coupling of LC (liquid chromatography) with NMR (nuclear magnetic resonance) spectroscopy can be considered now to be a standard analytical technique. Today, even more complex systems, which also include mass spectrometry (MS), are used. The question arises as to how such systems are handled efficiently with an increasing cost and a decreasing availability of skilled personal. LC-NMR and LC-NMR/MS combine the well-established techniques of LC, NMR and MS. For each of those techniques, various automation procedures and software packages are available and used in analytical laboratories. However, due to the necessary interfacing of such techniques, completely new demands occur and additional problems have to overcome. 

Wolfender, J.-L., Ndjoko, K. and Hostett mann, K., Liquid chromatography with ultraviolet absorbance-mass spectrometric detection and with nuclear magnetic resonance spectroscopy a powerful combination for the on-line structural investigation of plant metabolites, J. Chromatogr., A1000, 437-455 (2003). 

The IR spectrum provides little information about the hydrocarbon part of the compound. However, this is exactly the information provided by nuclear magnetic resonance spectroscopy, discussed in Chapter 14. The combination of these two types of spectroscopy is of enormous value in organic chemistry. 

Haberg A, Qu H, Haraldseth O, Unsgard G, Sonnewald U (1998) In vivo injection of [1-13C]glucose and [l,2-13C]acetate combined with ex vivo 13C nuclear magnetic resonance spectroscopy a novel approach to the study of middle cerebral artery occlusion in the rat. J Cereb Blood How Metab 18 1223-1232... 

The isolation of single substances has to be combined with a detailed characterization and structure elucidation. For this purpose, the following three techniques were mostly applied in the past Mass spectrometry, nuclear magnetic resonance spectroscopy, and X-ray crystallographic techniques. They will be discussed in more details in the following subsections. 

Two techniques that have found routine application in carbohydrate chemistry, namely, infrared and nuclear magnetic resonance spectroscopy, were reviewed in 1964 in combination, these methods can provide much of the information required for structural elucidation of an unknown compound. 

Structure determination of sapogenins and saponins from genus Astragalus originally involves a combination of chromatographic, chemical and spectral methods nuclear magnetic resonance spectroscopy (NMR) with chemical transformation and enzymatic degradation, as well as MS (mass spectroscopy). 

Sandvoss, M. Weltring, A. Preiss, A. Levsen, K. Wuensch, G. Combination of matrix solid-phase dispersion extraction and direct on-line chromatography-nuclear magnetic resonance spectroscopy-tandem mass spectrometry as a new efficient approach for the rapid screening of natural products Application to the total asterosaponin fraction of the starfish Asterias rubens. J. Chromatogr., A 2001, 917, 75-86. 

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