Water Humps

Quincy Teng (teng@sunchem.chem.uga.edu)
Fri, 21 Jul 1995 11:16:27 -0400 (EDT)

AMMRL Members -
We have problems with water suppression on our Bruker AMX-400
instrument for a long time. There are often a pair of humps
symmetric about the water peak with anti-phase to each other, no
matter how we shim the sample using different shimming methods.
Recently we use micro nmr tubes for protein samples. Sometimes
we get very nice water lineshape, sometimes not, even for the same
sample using same shimming file. A few days ago, I could not
eliminate the humps after a couple of hour shimming. So, I logged off
and left sample in the magnet. Next morning I started an 1 pulse
without changing anything. The water humps were gone. But I
saw huge water fid about 6 hours after I started a 1H-15N
experiment at 25C. The water humps disappeared again after the
AMX-400 has an overnight rest. I have repeated this for several
times. The water humps show up about 4-6 hours after starting an
experiment, and disappears after leaving the instrument idle
overnight. Could anyone let me know what can course the
instability? Is something wrong with the probe. If so, how can we
fix it (or have it fixed)?
Thanks a lot.

Quincy

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Quincy Teng
Director, Magnetic Resonance Facility
Department of Chemistry
University of Georgia
Athens, GA 30602
Phone: (706)542-1321
fax: (706)542-9454
INTERNET: teng@sunchem.chem.uga.edu
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