UW CHEMISTRY NMR

Dear Users

Some of you might have noticed the following but may have chosen to ignore this, since it didn’t affect your 1H spectra much.    The current TXO probe is not providing good 2H based shimming results and it needs some close attention.

Currently, the instrument can fail to give you good lineshape or Topshim can fail completely in cases such as CDCl3, where the Signal to Noise ratio of the 2H NMR signal is poor.  As a quick recap,  for the usual fully deuterated lock solvents we use,  the shim system relies on a good 2H NMR signal from the underlying lock solvent resonance.

For solvents such as Benzene-d6 or Acetone-d6,  the signal is strong enough to get a good Topshim result, even if there is an underlying hardware problem.   But weaker signals such as CDCl3 can fail completely and you might be left with poor lineshapes and ‘splittings’, where there is none expected.

Since the instrument is being used intensely,  I didn’t want to disrupt your immediate plans.  But I will address this in a planned maintenance session, soon.

Thank you for taking note.

NMR Facility Manager

8/13/2021