Hi Beth,
Also, when CDCl3 is old, it acidifes and becomes DCl. It decreases the CDCl3
lock signal intensity.
I always ask the users the age of the bottle and how it is kept when shimming
is a problem.
Good luck.
Simon
________________________________
> From: main_at_ammrl.groups.io on behalf of Feng Qiu viagroups.io
> Sent: Friday, January 17, 2025 4:58:24 PM
> To: main <main_at_ammrl.groups.io>
> Subject: Re: [AMMRL] "Topshim Failed: Signal to noise is too low"
Hi Beth,
I would check the 2H tuning and 2H 90 degree pulse.
Thanks,
Feng
On Friday, January 17, 2025 at 02:13:05 PM EST, Beth Moscato via groups.io wrote:
Hi everyone-
We have an AVANCE III (TS 3.7pl5) that’s been sporadically failing samples
saying that the signal to noise is too low. Most of the samples seem to be
marginal quality – usually CDCl3, sometimes with precipitate or water droplets –
but they often manage to successfully shim on our AV III HD spectrometer, and I’ve
noticed a dramatic uptick in the number of failures recently.
Note that most samples, including most samples in CDCl3, have successfully run in
TS. The TS data I’ve seen from the failed samples show a similar pattern to those
from normal samples (suggesting that the difference is quantitative and not qualitative).
I’ve done a 3D shim recently, but it hasn’t helped. The lock phase is set
appropriately.
Is there a way to increase the number of scans acquired in TS for specific solvents?
I’m not thrilled with it as a work around, but if it stops failing the samples,
that would be an improvement over the current situation.
Thank you!
Beth Moscato
Temple University
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Received on Fri Jan 17 2025 - 15:42:26 MST