Re: [AMMRL] Issue with shims on Agilent DD2 400 MHz

From: gafacey via groups.io <gafacey=gmail.com_at_groups.io>
Date: Tue, 1 Apr 2025 17:43:33 -0400
Hi Emily,
Could it be that the back pressure of helium in your magnet is significantly different since you installed you He recovery system?  The shims of the magnet can be very sensitive to this as can be seen here 
Resolution during He Fill
for data collected during a helium fill.   Have you tried remapping the shims since you installed the He recovery system?   If not, remapping may solve your problem. 

Good luck,
Glenn

On Apr 1, 2025, at 1:03 PM, Emily Crull via groups.io wrote:

Hi everyone,
 
I'm still working on familiarizing myself with VNMRJ 4, and our Agilent has recently encountered what is presenting as a shim based issue.
 
Over our spring break (Mar 16th-22nd), we had the hook up for our incoming He collection system installed (featured in the picture). Since that occurred, we have been having noticeably broader peaks in the 1H NMR spectra and simply running Z-gradient shims isn't fixing the issue. This is appearing even in the Ethylbenzene standard we have. We're just seeing humps with no resolved coupling at all.
 
 
Here's what I can say about the magnet itself:
  1. Based on the coin level I put on top of the bore, it is level, so the legs appear to be keeping up with the added weight from the install.
  2. The magnet is from 2012.
  3. We haven't seen a change in our Helium consumption. Our Nitrogen meter only registers in 5% increments and it's drop rate didn't change at all either.
  4. I believe I have updated the shim map using a house made D2O standard, but the issue still persists. The last shim map was from 2020.
  5. The default "Gradient shim" button in VNMRJ that appears next to the AutoLock and AutoTune is not improving the peak shape.
  6. Using the Autoshim drop down menu and selecting "Z-gradient and 4 non-spin shims" was sometimes resolving the issue.
  7. The issue is not limited to one account and is being observed on the admin account as well.
 
Any feedback on other ways to troubleshoot the issue and/or resolve it would be greatly appreciated. If any other information would be useful in diagnosing the problem, let me know what it is and I'll try and find it.
 
Many thanks,
Emily Crull
Director of Chemistry Shared Instrumentation
emily.crull_at_mail.wvu.edu
West Virginia University
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Received on Wed Apr 02 2025 - 04:21:52 MST

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