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  • 1
    Electronic Resource
    Electronic Resource
    Structure elucidation of β-carotene isomers by HPLC-NMR coupling using a C30 bonded phase (1997)
    Springer
    Fresenius' journal of analytical chemistry 357 (1997), S. 498-502 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The separation of cis/trans isomers of β-carotene has been performed with a C30 stationary phase employing 1H NMR spectroscopy as an on-line detection technique. 1D as well as 2D NMR spectra have been recorded in the stopped-flow mode for the predominant chromatographic peaks. Structural assignment of the five identified isomers was performed via comparison of simulated 1D 1H NMR spectra on the basis of the structures of β-carotene cis/trans isomers with the experimental data, and also by the analysis of the proton-proton connectivities in the 2D NMR spectra of three isomers with the highest concentration. The chromatographic retention behaviour of the isomers agreed well with previously reported data. The advantage of the applied hyphenated coupling technique compared to conventional off-line techniques lies in the fact that chromatographic separation and NMR detection are performed in a closed system, so that reisomerization of the separated compounds is inhibited.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160050200
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    On-Line Coupling of Separation Techniques to NMR (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 135-143 
    Details
    ISSN: 0935-6304
    Keywords: Chromatographic separation techniques ; High Performance Liquid Chromatography (HPLC) ; Gel Permeation Chromatography (GPC) ; Supercritical Fluid Chromatography (SFC) ; Capillary HPLC ; Nuclear Magnetic Resonance (NMR) spectroscopy ; hyphenation of chromatography with NMR spectroscopy ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The hyphenation of chromatographic separation techniques with NMR spectroscopy is one of the most powerful and time-saving methods for the separation and structural elucidation of unknown compounds and molecular compositions of mixtures. Most of the routinely used NMR flow-cells have detection volumes between 40-180 μL for conventional separations with analytical columns, and the newest designs employ detection volumes in the order of 200 nL for capillary separations. The low flow rates used in capillary chromatography permit the use of deuterated solvents. Unequivocal structural assignment of unknown chromatographic peaks is possible by two-dimensional stopped-flow capillary HPLC-NMR experiments.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
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