Hi All,
I have a problem that has been stumping me for some time, and has
perplexed a few Bruker engineers, as well.
We have a two-year old Bruker Avance 400 MicroBay with a QNP probe
running TopSpin 1.3 with the latest patch level under Windows2000 Pro.
We run it full time in IconNMR automation.
Intermittently, perhaps once or twice in a hundred spectra, we have a
peak doubling problem. It looks as if the lock jumps part way through
the experiment, such that the spectrum is run properly referenced, then
each peak has a shadow a few hundred Hertz off. The "jump" can vary from
a few dozen to a few hundred Hertz.
I have never been able to observe the phenomenon while running manually.
If the spectrum is run again under identical conditions it almost
certain to run properly.
The effect does not correlate with solvent type. It happens with any of
the solvents we use, and most commonly occurs with DMSO-d6, as that is
used most often. Temperature in the magnet and in the lab are
relatively stable. The effect has been seen in 1H & 13C spectra. It
might occur in 31P & 19F, too, but this instrument runs these nuclei
rarely.
Any suggestions as to the cause of this problem, and likely solutions,
would be very welcome.
Patrick Wheeler
Pfizer La Jolla Labs
Discovery Platform Chemistry
Chemical Analysis and Purification
Open Access Team
10770 Science Center Dr.
San Diego, CA 92121
858-526-4849 Office
858-395-2023 Mobile
858-678-8156 Fax
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Received on Tue Mar 21 2006 - 14:56:25 MST