Hello,
We have an Avance NEO with a Helium cryoprobe in our ~40-year-old unshielded
500 MHz magnet (vintage Oxford 500/51). Recently I've noticed that I
need to do a 3D shim more and more frequently. So I did a test: I 3D-shimmed
the magnet on the Solvent Suppression test sample (i.e. 2 mM sucrose, etc.,
90% H2O/10% D2O), wrote the shim file, inserted our test sample (sealed 30% Menthol
in CDCl3), locked, topshimmed (params: convcomp, ordmax and collected a 1D proton
without spinning. Everything looked good. 24 hours later, I inserted the Menthol
test sample, read the saved shim file, and collected a 1D proton without spinning
(using the same steps outlined above) and it looked like garbage. I collected
a 1D proton with spinning and the data improved a bit but didn't return to the quality
of the original spectrum.
If you have an ideas what might be going on, please let me know.
Thanks!
Wendy
*Wendy Breyer, Ph.D.*
Director of Instrumentation
Department of Chemistry
Lehigh University
6 E. Packer Ave.
Bethlehem, PA 18015
web216_at_lehigh.edu
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Received on Fri Aug 09 2024 - 17:14:44 MST