Suppressing Intense and Unwanted Signals
The functionality shown here is normally useful for proton spectra acquired in non-deuterated solvents. Suppose you have already presaturated or otherwise attenuated the solvent signal, yet you may need to completely remove it. A possible motivation may be that the solvent signal cannot be phase-corrected and therefore its tails cover the peaks of the substance of interest. The same technique removes any kind of signal. The mechanism is to filter signals away from the FID, according to their frequency. Working in time domain you circumvent the need to phase-correct the spectrum. Selectivity is never complete. Signals falling exactly at the frequency you specify are removed, while nearby peaks are attenuated.
You start selecting the command “Process/Suppress...”. iNMR asks you to specify 4 frequency values, yet you normally will furnish a single value (the leftmost field in the dialog). Then you modulate the selectivity of the filter. Try avoiding the extreme choices (4 and 40). Normally higher values give better results.
In the transformed spectrum, Ctrl-click the peak to suppress. Select “Suppress” from the contextual menu.