Improved excitation uniformity in multiple-quantum NMR experiments of mixtures

Multiple‐quantum 1H NMR spectroscopy has been finding a renewed interest for its possible applications in the analysis of mixtures of small molecules, due to its simplification properties. A crucial aspect of this application of multiple‐quantum NMR is the sensitivity of the spectrum intensity to th...

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Bibliographic Details
Published in:Magnetic resonance in chemistry 2013-04, Vol.51 (4), p.240-244
Main Authors: Manjunatha Reddy, G.N., Caldarelli, S.
Format: Article
Language:English
Subjects:
Chemical Sciences
Coupling (molecular)
Couplings
Excitation
Magnetic Resonance Spectroscopy - standards
MaxQ NMR
mixtures
multiple-quantum
NMR
NMR spectroscopy
Nuclear magnetic resonance
Organic Chemicals - chemistry
Organic chemistry
Parametrization
Quantum Theory
Reference Standards
Simplification
Spectra
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Summary:Multiple‐quantum 1H NMR spectroscopy has been finding a renewed interest for its possible applications in the analysis of mixtures of small molecules, due to its simplification properties. A crucial aspect of this application of multiple‐quantum NMR is the sensitivity of the spectrum intensity to the molecular structure and to the parameterization of the experiment, which could result in the missing of some components. We demonstrate that a general scheme to overcome this drawback consists in varying the experiment parameterizations over a small number of values, selected according the values of the couplings and the relaxation rates. Copyright © 2013 John Wiley & Sons, Ltd. The efficiency of multiple‐quantum experiments is highly dependent not only on the spin system details but also on the relaxation properties. This is particularly true in the presence of small couplings. We provide a scheme to produce more homogeneous multiple‐quantum spectra for mixtures of aromatic systems using co‐addition of multiple excitation delays, chosen according to the spin system characteristics and the observed signal lifetime.
ISSN:0749-1581
1097-458X
DOI:10.1002/mrc.3938