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Selective diffusion spectroscopy using excitation sculpting
Author(s) -
Howe Peter W. A.
Publication year - 2017
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.4402
Subject(s) - chemistry , excitation , diffusion , spectroscopy , nuclear magnetic resonance spectroscopy , pulse sequence , resonance (particle physics) , spectral line , analytical chemistry (journal) , minor (academic) , nuclear magnetic resonance , molecular physics , atomic physics , physics , thermodynamics , organic chemistry , quantum mechanics , astronomy , chromatography , political science , law
Diffusion spectroscopy NMR provides a sensitive and fast way of determining diffusion coefficient. The coefficient is measured by fitting attenuation of resonance intensities to the Stejskal–Tanner equation, but, because it is an exponential equation, this fitting is quite sensitive to experimental artefacts. Intense resonances in NMR spectra, such as solvent signals, are a particular problem because small fractions of intensity of the intense resonances can significantly change the intensities of minor resonances and distort their calculated diffusion coefficients. This problem can be overcome by selective excitation of only the minor resonances, and the method of choice for this is excitation sculpting. This paper shows that the conventional excitation sculpting pulse sequence can be used directly for DOSY spectroscopy with minimal modification. The sequence suppresses intense resonances very effectively, allowing the reproducible measurement of diffusion coefficients of minor solutes in a solvent containing five separate resonances. It is sensitive and robust to convection. Excitation sculpting will allow the application of diffusion spectroscopy to samples which include multiple intense resonances, such as polymeric solvents. Copyright © 2015 John Wiley & Sons, Ltd.