Nuclear magnetic resonance spectrometry, determination

A. Nordon, C. Meunier, R.H. Carr, P.J. Gemperline, and D. Littlejohn, Determination of the ethylene oxide content of polyether polyols by low-field H nuclear magnetic resonance spectrometry. Anal. Chim. Acta, 472, 133-140... 

Wilkes, J. S., Levisky, J. A., Pflug, J. L. et al.. Composition determinations of liquid chloroaluminate molten-salts by nuclear magnetic-resonance spectrometry, Anal. Chem., 54,2378, 1982. 

International Standard Organization (ISO) 10565. 1999. Oilseeds-Simultaneous Determination of Oil and Moisture Contents - Method Using Pulsed Nuclear Magnetic Resonance Spectrometry. International Organization for Standardization, Geneva. 

T. Renukappa, G. Roos, I. Klaiber, B. Vogler, and W. Kraus, Application of high-performance liquid chromatography coupled to nuclear magnetic resonance spectrometry, mass spectrometry and bioassay for the determination of active saponins from Bacopa Monniera Wettst.,7. Chromatogr. A 847 (1999), 109-116. 

Nuclear magnetic resonance spectrometry has been employed for the determination of various sulfonamides using a 5% NaOD solution in... 

Nuclear Magnetic Resonance spectrometry is used for many types of analytical work but is key in the elucidation of structures of chemical compounds. When used in conjunction with mass spectrometry and infrared spectroscopy, the three techniques make it possible to determine the complete structures of novel compounds. Mass spectrometry is used to determine the size of a molecule and its molecular formula and infrared spectroscopy help identify the functional groups present in a molecule. NMR spectroscopy is used to determine the carbon-hydrogen framework of a molecule and works with even the most complex molecules. NMR is now being used to elucidate complicated protein structures ... 

O Neill, I.K., Sargent, M., Trimble, M.L. (1980). Determination of phytate in foods by phosphorus-31 Fourier transform nuclear magnetic resonance spectrometry. Anal. Chem., 52, 1288. 

Describe the fundamentals of the method and basic physical principles underlying nuclear magnetic resonance spectrometry as applied to protein structure determination. 

NMR (or NUCLEAR MAGNETIC RESONANCE SPECTROMETRY). A method for structure determination of organic compounds based on the magnetic properties of different nuclei. 

In addition, before the routine use of instrumentation such as gas-liquid chromatography, infrared spectroscopy, nuclear magnetic resonance spectrometry, etc., the identity of components and compositions were determined by isolation. The latter involved the problems of separating compounds of closely related properties. This often explains conflicting and inaccurate data published in the literature. The modern techniques of determining compositions have resolved some of these problems. 

The determination of the content of oxyethylene groups in ethylene oxide - propylene oxide can also easily be carried out by nuclear magnetic resonance spectrometry [93, 100] withont chemical splitting of the ether linkage. However, it is difficult to identify the base componnds by this method. A number of methods for the cleavage of ethers have been stndied bnt few were applied to the identification of the base compounds of the polyurethane polyethers. 

Amino groups have also been acetylated with acetic anhydride in dimethylacetamide. Diethylamine was added, and the excess amine was titrated potentiometrically. The sequence distribution of an aromatic polyamide terpolymer prepared under various reaction conditions was determined by nuclear magnetic resonance spectrometry. Infrared spectroscopy and mass spectrometry have been used to estimate the degree of conversion of polyimides, ie. the extent of polyamic acid ring closure. 

International Standard Organization ISO 5511-1992. Oilseeds—Determination of Oil Content—Method using Continuous-Wave Low-Resolution Nuclear Magnetic Resonance Spectrometry (Rapid method). Re-approved in 1997. 

Ho FF-L, Kohler RR, Ward GA (1972) Determination of molar substitution and degree of substitution of hydroxypropyl cellulose by nuclear magnetic resonance spectrometry. Anal Chem 44 178-181... 

Nuclear magnetic resonance spectrometry has solved so many problems that one would hope it could be applied to the determination of aliphatic weak bases. Taft and Levins (338) have succeeded in using this method through the effect of protonation on the fluorine resonance of several p-fluorinated bases. Unfortunately, the flu-orinated aromatic system is required and also a relatively concentrated solution of indicator so that the use of aqueous acid is ruled out. In acetic-sulfuric acid solutions Taft finds serious medium effects for Hammett indicators but sharp titration curves for car-bonium ion bases. This result is in complete agreement with the conclusions described previously (II-D) for solvation of carbonium ions compared to other onium ions. 

Present day techniques for structure determination in carbohydrate chemistry are sub stantially the same as those for any other type of compound The full range of modern instrumental methods including mass spectrometry and infrared and nuclear magnetic resonance spectroscopy is brought to bear on the problem If the unknown substance is crystalline X ray diffraction can provide precise structural information that m the best cases IS equivalent to taking a three dimensional photograph of the molecule... 

Ideally, a mass spectmm contains a molecular ion, corresponding to the molecular mass of the analyte, as well as stmcturaHy significant fragment ions which allow either the direct deterrnination of stmcture or a comparison to Hbraries of spectra of known compounds. Mass spectrometry (ms) is unique in its abiUty to determine direcdy the molecular mass of a sample. Other techniques such as nuclear magnetic resonance (nmr) and infrared spectroscopy give stmctural information from which the molecular mass may be inferred (see Infrared technology and raman spectroscopy Magnetic spin resonance). 

Analytical methods iaclude thin-layer chromatography (69), gas chromatography (70), and specific methods for determining amine oxides ia detergeats (71) and foods (72). Nuclear magnetic resonance (73—75) and mass spectrometry (76) have also been used. A frequentiy used procedure for iadustrial amine oxides (77) iavolves titratioa with hydrochloric acid before and after conversion of the amine to the quaternary ammonium salt by reaction with methyl iodide. A simple, rapid quaHty control procedure has been developed for the deterrniaation of amine oxide and unreacted tertiary amine (78). 

The melting points, optical rotations, and uv spectral data for selected prostanoids are provided in Table 1. Additional physical properties for the primary PGs have been summarized in the Hterature and the physical methods have been reviewed (47). The molecular conformations of PGE2 and PGA have been determined in the soHd state by x-ray diffraction, and special H and nuclear magnetic resonance (nmr) spectral studies of several PGs have been reported (11,48—53). Mass spectral data have also been compiled (54) (see Mass spectrometry Spectroscopy). 

Among the modem procedures utilized to estabUsh the chemical stmcture of a molecule, nuclear magnetic resonance (nmr) is the most widely used technique. Mass spectrometry is distinguished by its abiUty to determine molecular formulas on minute amounts, but provides no information on stereochemistry. The third most important technique is x-ray diffraction crystallography, used to estabUsh the relative and absolute configuration of any molecule that forms suitable crystals. Other physical techniques, although useful, provide less information on stmctural problems. 

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... 

Determining the structure of an organic compound was a difficult and time-consuming process in the 19th and early 20th centuries, but powerful techniques are now available that greatly simplify the problem. In this and the next chapter, we ll look at four such techniques—mass spectrometry (MS), infrared (IR) spectroscopy, ultraviolet spectroscopy (UV), and nuclear magnetic resonance spectroscopy (NMR)—and we U see the kind of information that can be obtained from each. 

We saw in Chapter 12 that mass spectrometry gives a molecule s formula and infrared spectroscopy identifies a molecule s functional groups. Nuclear magnetic resonance spectroscopy does not replace either of these techniques rather, it complements them by "mapping" a molecule s carbon-hydrogen framework. Taken together, mass spectrometry, JR, and NMR make it possible to determine the structures of even very complex molecules. 

Mass spectrometry, infrared spectroscopy, and nuclear magnetic resonance spectroscopy are techniques of structure determination applicable to all organic molecules. In addition to these three generally useful methods, there s a fourth—ultraviolet (UV) spectroscopy—that is applicable only to conjugated systems. UV is less commonly used than the other three spectroscopic techniques because of the specialized information it gives, so we ll mention it only briefly. 

The development and reports of methods for colorless chlorophyll derivative (RCCs, FCCs, and NCCs) analysis are relatively recent and the structures of the compounds are being elucidated by deduction from their chromatographic behaviors, spectral characteristics (UV-Vis absorbance spectra), mass spectrometry, and nuclear magnetic resonance analysis. The main obstacle is that these compounds do not accumulate in appreciable quantities in situ and, moreover, there are no standards for them. The determination of the enzymatic activities of red chlorophyll catabolite reductase (RCCR) and pheophorbide a monoxygenase (PAO) also helps to monitor the appearance of colorless derivatives since they are the key enzymes responsible for the loss of green color. ... 

Several modem analytical instruments are powerful tools for the characterisation of end groups. Molecular spectroscopic techniques are commonly employed for this purpose. Nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy and mass spectrometry (MS), often in combination, can be used to elucidate the end group structures for many polymer systems more traditional chemical methods, such as titration, are still in wide use, but employed more for specific applications, for example, determining acid end group levels. Nowadays, NMR spectroscopy is usually the first technique employed, providing the polymer system is soluble in organic solvents, as quantification of the levels of... 

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