This is a processing technique which was presented in a poster at the 1994 ENC by Ken Metz (Poster # WP111) entitled "Simple Technique for Improving Resolution in Heteronuclear NMR Spectra by Deconvolution with the Measured B0 Field Distribution". The poster demonstrated a processing technique for removing lineshape distortions, based on an earlier paper by Morris (J.Magn.Reson., 80, 547, 1988 ) and showed some impressive improvements in lineshape.
The basic idea is that if you know the shape of the distortion, you should be able to correct for it. To measure the distortion, you need a "reference" spectrum of a single, isolated peak whose ideal lineshape is known, eg., chloroform or water. A comparison of the reference spectrum and the ideal lineshape characterizes the shape of the distortion. Both ideal and reference peaks are mathematically adjusted to be at zero frequency and then inverse FTed. An apodization function is created by dividing the ideal time-domain function by the reference FID. This apodization function is then applied to a real FID. The resulting lineshapes are substantially improved. The whole approach, of course, relies on the assumption that all peaks have the same distortion.
After adding this capability to NUTS, we tested it on a proton spectrum acquired with a 5mm 13C probe which was never intended for proton observation, for good reason. The lineshape starting at about 2% is asymmetrical, and gets truly ugly below that. The goal was to see if reference deconvolution would yield acceptable proton spectra from data acquired with this probe. A sample of H2O/D2O run separately was used as the reference and the ideal lineshape used was a 0.5 Hz Lorentzian. While the corrected lineshapes aren’t perfect, they are substantially improved. The integral had to be corrected for a small amount of distortion at the base of the peaks, but yielded the expected ratios. The results are encouraging, even for this extreme case.
See also: How to apply reference deconvolution in NUTS.
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Last updated: 01/21/03