Charlie,
We had a similar problem and it turned out that the "standard" mode of
operation for carbon acquisition in automation is to have a signal noise
test after which acquistion stops if the signal to noise is sufficient. I
believe this is really stupid (any Varian people listening?) since the
solvent peak is often the largest in the spectrum and the acquistion will
abort even if you have poor signal from the actual sample. It probably
"fails" for methanol, since the 13C signal is more intense than chloroform.
If you open the customization dialog boxes, you can change the option to
"DO NOT TEST". To change the default setting, set wbs in the standard
parameter set from wbs='testsn' to wbs=''. Furthermore, you should change
the order of the options in vnmrsys/dialoglib/CARBON/acquire.def such that
"DO NOT TEST" is first rather than second, otherwise the signal to noise
test will be set to "on" any time you customize an acquistion run.
I hope that helps.
John L. Battiste, Senior Analytical Chemist
3M Pharmaceuticals
3M Center, Bldg. 270-4S-02
St. Paul, MN 55144-1000
Tel: 651-736-8298
Fax: 651-736-3974
jlbattiste_at_mmm.com
----- Forwarded by Robb J. Webb/US-Corporate/3M/US on 12/05/03 07:16 AM
-----
Dear AMMRL-istas
My Unity Inova works great in open access using CustomQ. However, recently
some overnite carbon runs have failed for my students. The macros are set
for 12000 scans and this functions properly for CDCL3. When CD3OD is the
solvent, the acquisition terminates after 512 pulses, reproducibly, with a
message saying acquisition aborted. I have sat a watched it, and it seems
real.
Is this a receiver overflow caused by the large 13C signal from
deuteromethanol?
Is there something I should look at specifically?
Any suggestions gratefully received,
Charlie DeBrosse
Temple University
Received on Fri Dec 05 2003 - 18:34:32 MST