期刊
JOURNAL OF MAGNETIC RESONANCE
卷 208, 期 2, 页码 270-278出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jmr.2010.11.012
关键词
NMR; H-1 DOSY; Diffusion-ordered spectroscopy; Diffusion; Oneshot; J-modulation; Phase distortions; Purging pulse
资金
- Engineering and Physical Sciences Research Council [EP/D05592X, EP/E05899X/1, EP/E057888/1]
- Engineering and Physical Sciences Research Council [EP/E05899X/1, EP/E057888/1] Funding Source: researchfish
- EPSRC [EP/E057888/1, EP/E05899X/1] Funding Source: UKRI
Diffusion-ordered spectroscopy (DOSY) is a powerful NMR method for identifying compounds in mixtures. DOSY experiments are very demanding of spectral quality; even small deviations from expected behaviour in NMR signals can cause significant distortions in the diffusion domain. This is a particular problem when signals overlap, so it is very important to be able to acquire clean data with as little overlap as possible. DOSY experiments all suffer to a greater or lesser extent from multiplet phase distortions caused by J-modulation, requiring a trade-off between such distortions and gradient pulse width. Multiplet distortions increase spectral overlap and may cause unexpected and misleading apparent diffusion coefficients in DOSY spectra. These effects are described here and a simple and effective remedy, the addition of a 45 degrees purging pulse immediately before the onset of acquisition to remove the unwanted anti-phase terms, is demonstrated. As well as affording significantly cleaner results, the new method allows much longer diffusion-encoding pulses to be used without problems from J-modulation, and hence greatly increases the range of molecular sizes that can be studied for coupled spin systems. The sensitivity loss is negligible and the added phase cycling is modest. The new method is illustrated for a widely-used general purpose DOSY pulse sequence, Oneshot. (C) 2010 Elsevier Inc. All rights reserved.
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