Probable causes of bad shimming in NMR spectrometers
This is to remind myself what all could be done if there is bad shimming issue next time (coming from bad shimming issue a couple of times at our 600 MHz spectrometer that led to engaging Bruker engineers to resolve the issue):
- Make sure no dust particle/tissue paper flake etc. falls in the probe head (may come from unclean NMR tube, paint peeling off from ceiling, dust getting trapped in the room due to air dynamics etc). Solution: Clean the probe preferably in presence of an expert!
- If you are running on pneumatic leg systems, make sure that all three legs are balanced.
- There may be a leak in the vacuum in cryo-platform pump.
- If using Shigemi tubes, a small precipitate in the tube may come in the coil range and result in bad shim.
- If NMR tubes are susceptibility matched to a particular solvent (say H2O/D2O), do not try putting in any other solvent and shimming, it may disturb all the shim values.
- If you come to think of any other point, please put that in the comment, I will update this list accordingly. Thanks.
Uncategorized | cjeet | 
December 16, 2015 5:38 am