Nuclear magnetic resonance chromatographic

The side-chain chlorine contents of benzyl chloride, benzal chloride, and benzotrichlorides are determined by hydrolysis with methanolic sodium hydroxide followed by titration with silver nitrate. Total chlorine determination, including ring chlorine, is made by standard combustion methods (55). Several procedures for the gas chromatographic analysis of chlorotoluene mixtures have been described (56,57). Proton and nuclear magnetic resonance shifts, characteristic iafrared absorption bands, and principal mass spectral peaks have been summarized including sources of reference spectra (58). Procedures for measuring trace benzyl chloride ia air (59) and ia water (60) have been described. 

Abscisin II is a plant hormone which accelerates (in interaction with other factors) the abscission of young fruit of cotton. It can accelerate leaf senescence and abscission, inhibit flowering, and induce dormancy. It has no activity as an auxin or a gibberellin but counteracts the action of these hormones. Abscisin II was isolated from the acid fraction of an acetone extract by chromatographic procedures guided by an abscission bioassay. Its structure was determined from elemental analysis, mass spectrum, and infrared, ultraviolet, and nuclear magnetic resonance spectra. Comparisons of these with relevant spectra of isophorone and sorbic acid derivatives confirmed that abscisin II is 3-methyl-5-(1-hydroxy-4-oxo-2, 6, 6-trimethyl-2-cyclohexen-l-yl)-c s, trans-2, 4-pen-tadienoic acid. This carbon skeleton is shown to be unique among the known sesquiterpenes. 

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. ... 

U.Tallarek, E. Bayer, G. Guiochon 1998, (Study of dispersion in packed chromatographic columns by pulsed field gradient nuclear magnetic resonance), J. Am. Chem. Soc. 120, 1494. 

Fourier transform infrared (FTIR) spectroscopy, 13C nuclear magnetic resonance (NMR) spectroscopy, ultraviolet-visible (UV-VIS) and fluorescence spectroscopy can be integrated with chromatographic techniques especially in the study of ageing and degradation of terpenic materials. They can be used to study the transformation, depletion or formation of specific functional groups in the course of ageing. 

Modern spectroscopy plays an important role in pharmaceutical analysis. Historically, spectroscopic techniques such as infrared (IR), nuclear magnetic resonance (NMR), and mass spectrometry (MS) were used primarily for characterization of drug substances and structure elucidation of synthetic impurities and degradation products. Because of the limitation in specificity (spectral and chemical interference) and sensitivity, spectroscopy alone has assumed a much less important role than chromatographic techniques in quantitative analytical applications. However, spectroscopy offers the significant advantages of simple sample preparation and expeditious operation. 

Enantiomers have identical chemical and physical properties in the absence of an external chiral influence. This means that 2 and 3 have the same melting point, solubility, chromatographic retention time, infrared spectroscopy (IR), and nuclear magnetic resonance (NMR) spectra. However, there is one property in which chiral compounds differ from achiral compounds and in which enantiomers differ from each other. This property is the direction in which they rotate plane-polarized light, and this is called optical activity or optical rotation. Optical rotation can be interpreted as the outcome of interaction between an enantiomeric compound and polarized light. Thus, enantiomer 3, which rotates plane-polarized light in a clockwise direction, is described as (+)-lactic acid, while enantiomer 2, which has an equal and opposite rotation under the same conditions, is described as (—)-lactic acid. 

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. 

Following hits, the lead compounds are purihed using chromatographic techniques and their chemical compositions are identihed via spectroscopic and chemical means. Structures may be elucidated using X-ray or nuclear magnetic resonance (NMR) methods. 

Low-resolution nuclear magnetic resonance spectroscopy can also be used to determine percent by weight hydrogen in jet fuel (ASTM D3701) and in light distillate, middle distillate, and gas-oil (ASTM D4808). As noted above, chromatographic methods are not applicable to naphtha, where losses can occur by evaporation. 

Meyer, C., Skogsberg, U., Welsch, N., and Albert, K., Nuclear magnetic resonance and high-performance liquid chromatographic evaluation of polymer-based stationary phases immobilized on silica. Anal. Bioanal. Chem., 382, 679, 2005. 

SenteU, K.B., Nuclear-magnetic-resonance and electron-spin-resonance spectroscopic investigations of reversed-phase liquid-chromatographic retention mechanisms—stationary-phase structure, J. Chromatogr. A, 656, 231, 1993. 

Gilpin, R.K. and Gangoda, M.E., Nuclear magnetic resonance spectrometry of alkyl ligands immobilized on reversed phase liquid chromatographic surfaces, Anal. Chem., 56, 1470, 1984. 

T Hyphenated Chromatographic Techniques in Nuclear Magnetic Resonance Spectroscopy... 

Examines hyphenated chromatographic techniques with nuclear magnetic resonance spectroscopy... 

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