Hello Vernon
DMF is a tricky solvent to run gradient shimming on. The signal picked for
shimming is one of the methyl groups which are less than 0.2 ppm apart. In
order to only excite this one signal a selective pulse is applied to it. The
duration of this pulse is given by the parameter SELWID in the solvent specific
parameters. For DMF this is set to 0.15 ppm
It looks like under these conditions the pulse length gets to be over 1 second
and the deuterium amplifier does not like this.
You can specify other parameters to be used with a solvent in automation.
You can try the formyl signal at 8.61 ppm. It will be less intensive but
should still work. The command would then look somethig like "topshim 2h
o1p=8.61 selwid=1.0"
Or you can just try "topshim selwid=0.2" but there is a risk that it catches
too much of the other methyl group and the results are going to be bad.
With best regards
Clemens
On 2/20/2026 3:55 PM, Vernon M Russell via groups.io wrote:
I don't run DMF experiments very often but today I received the following
error when topshim was running in automation mode on a sample dissolved in
DMF.
BSMS Error:
L-TRX 2H Amplifier: RF Pulse Length or Duty Cycle violation! Please check
your Pulse Program. Max Duty Cycle: 10%, Max Pulse Length: 1000ms
I have not made any changes to the standard ICON-NMR settings for Topshim
nor the DMF listing in edlock. The sample eventually shims okay and data
collected for the sample. Any help would be appreciated.
Thanks,
Vernon Russell
vrussell_at_wlgore.com
T +1-410-506-3852
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Received on Wed Feb 25 2026 - 10:54:54 MST