Nuclear magnetic resonance spectroscopy coupling

Nuclear Magnetic Resonance Spectroscopy Coupling Constants... 

Albert, K. 1997. Supercritical fluid chromatography— proton nuclear magnetic resonance spectroscopy coupling. Journal of Chromatography A, 785 65-83. 

Nuclear Magnetic Resonance Spectroscopy. Nmr is a most valuable technique for stmeture determination in thiophene chemistry, especially because spectral interpretation is much easier in the thiophene series compared to benzene derivatives. Chemical shifts in proton nmr are well documented for thiophene (CDCl ), 6 = 7.12, 7.34, 7.34, and 7.12 ppm. Coupling constants occur in well-defined ranges J2-3 = 4.9-5.8 ... 

Pusecker K, J Schewitz, P Gfrorer, L-H Tseng, K Albert, E Bayer (1998) On-line coupling of capillary electrochromatography, capillary electrophoresis, and capillary HPLC with nuclear magnetic resonance spectroscopy. Anal Chem 70 3280-3285. 

Abel, C.B.L., Lindon, J.C., Noble, D., Rudd, B.A.M., Sidebottom, P.J., and Nicholson, J.K, Characterization of metabolites in intact Streptomyces citricolor culture supernatants using high-resolution nuclear magnetic resonance and directly coupled high-pressure liquid chromatography-nuclear magnetic resonance spectroscopy, Anal. Biochem., 270, 220, 1999. 

Riickert, M., Wohlfarth, M., and Bringmann, G., Characterization of protein mixtures by ion-exchange chromatography coupled on-line to nuclear magnetic resonance spectroscopy, ]. Chromatogr. A, 840, 131, 1999. 

V. Wray, Carbon-carbon coupling constants a compilation of data and a practical guide. In Progress in Nuclear Magnetic Resonance Spectroscopy 1979, Vol. 13, 1979, pp. 177-256. 

J.-L. Wolfender, S. Rodriguez and K. Hostettmann, Liquid chromatography coupled to mass spectrometry and nuclear magnetic resonance spectroscopy for the screening of plant constituents. J. Chromatogr.A 794 (1998) 299-316. 

A structure-based approach for discovering protein ligands and for drug design by coupling size exclusion chromatography, mass spectrometry, and nuclear magnetic resonance spectroscopy. Anal. Chem. 2001, 73, 571-581. 

De Rijke, E. et al.. Liquid chromatography coupled to nuclear magnetic resonance spectroscopy for the identification of isoflavone glucoside malonates in T. pratense L. leaves, J. Sep. Sci., 27, 1061, 2004. 

The flame retardant mechanism of PC/ABS compositions using bisphenol A bis(diphenyl phosphate) (BDP) and zinc borate have been investigated (54). BDP affects the decomposition of PC/ABS and acts as a flame retardant in both the gas and the condensed phase. The pyrolysis was studied by thermogravimetry coupled with fourier transform infrared spectroscopy (FUR) and nuclear magnetic-resonance spectroscopy. Zinc borate effects an additional hydrolysis of the PC and contributes to a borate network on the residue. 

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. 

This article treats the benefits, possibilities and drawbacks of supercritical fluid chromatography (SFC) and supercritical fluid extraction (SFE) coupled to nuclear magnetic resonance spectroscopy. After a general overview and consideration of the motivation for such techniques, the design of high-pressure flow probes, as well as the principle experimental set-ups, are described. By means of several applications and comparison to HPLC-NMR, the utility of these hyphenated techniques is demonstrated. 

Nuclear magnetic resonance spectroscopy (NMR) is one of the most powerful analytical methods for identification and structure elucidation of organic compounds. Since NMR spectra are recorded in solution, no phase transfer like in MS is necessary when coupled with LC techniques. Additionally, NMR is a non-destructive detection technique, allowing the analyte to be transferred for characterization using additional methods. As of today, LC—NMR coupling was used in a wide range of applications [65,66,67,68,69,70,71],... 

Nuclear Magnetic Resonance Spectroscopy. Nmr is a most valuable technique for structure determination in thiophene chemistry, especially because spectral interpretation is much easier in the thiophene series compared to benzene derivatives. Chemical shifts in proton nmr are well documented for thiophene (CDC13), 6 = H2 7.12, H3 7.34, H4 7.34, and H5 7.12 ppm. Coupling constants occur in well-defined ranges J2 3 = 4.9-5.8 J3 4 = 3.45-4.35 J2 4 = 1.25-1.7 and J2 5 = 3.2-3.65 Hz. The technique can be used quantitatively by comparison with standard spectra of materials of known purity. 13C-nmr spectroscopy of thiophene and thiophene derivatives is also a valuable technique that shows well-defined patterns of spectra. 13C chemical shifts for thiophene, from tetramethylsilane (TMS), are C2 127.6, C3 125.9, C4 125.9, and C5 127.6 ppm. 

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