NMR chromatography

An important technical development of the PFG and STD experiments was introduced at the beginning of the 1990s the Diffusion Ordered Spectroscopy, that is DOSY.69 70 It provides a convenient way of displaying the molecular self-diffusion information in a bi-dimensional array, with the NMR spectrum in one dimension and the self-diffusion coefficient in the other. While the chemical-shift information is obtained by Fast Fourier Transformation (FFT) of the time domain data, the diffusion information is obtained by an Inverse Laplace Transformation (ILT) of the signal decay data. The goal of DOSY experiment is to separate species spectroscopically (not physically) present in a mixture of compounds for this reason, DOSY is also known as "NMR chromatography."... 

PGSE diffusion measurements can also be presented as a 2D spectrum where the chemical shift is displayed in the first dimension and the diffusion coefficient in the second one. Such an experiment is called DOSY (Diffusion Ordered Spectroscopy) [274, 322, 323] and has also been referred to as NMR chromatography , for its ability to facilitate and visualize the resolution and assignment of complex mixtures. Although used in several areas of chemistry, such as micelles [324], polymers [325-328], resins [329], biochemistry [330-332] and organic chemistry [333-336],... 

In most cases, small to medium-sized industries, unless they have a broad base, cannot and do not have expertise in many areas of science, nor the funds, to set up and operate expensive "Library of Instruments" centers such as electron microscopy, NMR, chromatography-mass spectrometry, automated chemical systems, plasma spectroscopy, bioengineering technology, complex animal centers, and engineering systems. Many specialists are at universities. In a university-industry cooperative research venture, the goals of the research problem can be mutual, even though the missions of the institutions are different. 

Turbidity titration Viscosity, light scattering, FT-IR Chemical degradation, NMR, chromatography... 

Y. Nishiyama, M.H. Frey, S. Mukasa, H. Utsumi, solid-state NMR chromatography by magic angle spinning Ti relaxation ordered spectroscopy, J. Magn. Reson. 

See also Biofluids Studied by NMR Cells Studied by NMR Chromatography-NMR, Applications In vivo NMR, Applications, In vivo NMR, Applications, Other Nuclei NMR Perfused Organs Studied Using NMR Spectroscopy Solvent Suppression Methods in NMR Spectroscopy. 

Other techniques for predicting the cetane number rely on chemical analysis (Glavinceski et al., 1984) (Pande et al., 1990). Gas phase chromatography can be used, as can NMR or even mass spectrometry (refer to 3.2.1.l.b and 3.2.2.2). 

Dorn H C 1984 H NMR—a new detector for liquid chromatography Anal. Chem. 56 747A-58A... 

The General Tests and Assays. This section of the USP gives methods for tests that are general in nature and apply to a number of the substances. Procedures are iacluded for such tests as heavy metals, melting point, chloride, sulfate, sterility, bacterial endotoxins, and pyrogens. Also iacluded are descriptions of various analytical techniques, such as spectrophotometry, chromatography, and nmr, and descriptions of tests to be used on glass or plastic containers, mbber closures, etc. 

Poly(ethylene oxide). The synthesis and subsequent hydrolysis and condensation of alkoxysilane-terniinated macromonomers have been studied (39,40). Using Si-nmr and size-exclusion chromatography (sec) the evolution of the siUcate stmctures on the alkoxysilane-terniinated poly(ethylene oxide) (PEO) macromonomers of controlled functionahty was observed. Also, the effect of vitrification upon the network cross-link density of the developing inorganic—organic hybrid using percolation and mean-field theory was considered. 

To determine the phosphoHpid and fatty acid compositions chromatographic methods (28) like gas chromatography (gc), thin-layer chromatography (tic), and high performance Hquid chromatography (hlpc) are used. Newer methods for quantitative deterrnination of different phosphoHpid classes include P-nmr (29). 

Finally, the techniques of nmr, infrared spectroscopy, and thin-layer chromatography also can be used to assay maleic anhydride (172). The individual anhydrides may be analyzed by gas chromatography (173,174). The isomeric acids can be determined by polarography (175), thermal analysis (176), paper and thin-layer chromatographies (177), and nonaqueous titrations with an alkaU (178). Maleic and fumaric acids may be separated by both gel filtration (179) and ion-exchange techniques (180). 

Hydroxyl number and molecular weight are normally determined by end-group analysis, by titration with acetic, phthaUc, or pyromellitic anhydride (264). Eor lower molecular weights (higher hydroxyl numbers), E- and C-nmr methods have been developed (265). Molecular weight deterrninations based on coUigative properties, eg, vapor-phase osmometry, or on molecular size, eg, size exclusion chromatography, are less useful because they do not measure the hydroxyl content. 

Instmmental methods of analysis provide information about the specific composition and purity of the amines. QuaUtative information about the identity of the product (functional groups present) and quantitative analysis (amount of various components such as nitrile, amide, acid, and deterruination of unsaturation) can be obtained by infrared analysis. Gas chromatography (gc), with a Hquid phase of either Apiezon grease or Carbowax, and high performance Hquid chromatography (hplc), using siHca columns and solvent systems such as isooctane, methyl tert-huty ether, tetrahydrofuran, and methanol, are used for quantitative analysis of fatty amine mixtures. Nuclear magnetic resonance spectroscopy (nmr), both proton ( H) and carbon-13 ( C), which can be used for quaHtative and quantitative analysis, is an important method used to analyze fatty amines (8,81). 

Purifications of elfamycins have been described in the Hterature using Craig distribution (2,34), chromatography on Sephadex LH-20 (2,14,26) and Amberlite XAD-2 (10,17,19,26), supercritical fluid extraction (37), and chromatography on an Ito multilayer cod planet centrifuge (26,38). and nmr assignments of most elfamycins have been accompHshed (3,24,26,32). The characteristic uv spectra permits some differentiation (12) and bathochromic shifts associated with Al " complexation have been used to quantify efrotomycin (2, R = CH ) in feed premixes (39,40). 

The separation and analysis of 1-propanol are straightforward. Gas chromatography is the principal method employed. Other iastmmental techniques, eg, nmr, ir, and classical organic quaHtative analysis, are useful. Molecular sieves (qv) have been used to separate 1-propanol from ethanol and methanol. Commercial purification is accompHshed by distillation (qv). 

Most common analytical methods for analysis of the major component or minor components of organic products are used for pyridines. These include gas chromatography, titration, free2ing point, nmr, in, hplc, and gc/ms. 

More recendy the cis and trans isomers of the mosquito repellent CIC-4, a mixture of citroneUa isomers, have been separated by preparative hplc and bioassayed for effectiveness (23). Chiral-phase capillary gas chromatography and mosquito repellent activity of some oxazoUdine derivatives of (+)-and ( —)-citroneUal have been studied to find stmcture—activity relationships (24). Several 2-aLkyl- -acetyloxahdines have been synthesized and tested against mosquitoes, with further efforts using nmr to determine the rotational isomers of the more active N-acetyl-2,2-dimethyloxazohdine (25). 

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