Notes:
Concerning setting up the system for gradient shimming, it’s not necessary to calibrate on each solvent and a map is not made for each solvent. However, it is necessary to make standard and selective maps for solvents that have a single resonance and multiple resonances.
- 3D shim the system using the 1H lineshape sample. The non-spinning linewidth is pretty good at ~0.5/6/9 Hz
- saved these shims as the system shims (as console user)
- For different solvents (acetone-d6, D2O, benzene-d6, CDCl3) set the system to do 1D homospoil shimming (not fast_homospoil, which does not give as good shimming).
The setup is a bit harder than it needs to be (unless there is a way to do it that I don’t know about) and requires you to open the 1D gradient shimming panel with a different sample/solvent and then set the parameters to use for gradient shimming using that solvent, making sure that you uncheck the option “Use for this sample only”, enter the console login credentials and then set the parameters
- Solvents like THF and toluene-d8 have more than one deuterium resonance so require the use of selective homospoil shimming. If no maps for that method existed, create them by changing the solvent for one of the samples to THF and then making some selective homospoil maps as the console user. Then selected these maps for samples that had THF or toluene as the solvent.
First do Manual Shim in Datum user. (Some extra utilities available in user Datum that is not in Console.)
Load your sample as Datum. Do a Fast non spin and spin shim. Run [Globa], Utilities, [Autoshim] -with Radial Shims’
Do a 3D Gradient Shim on, X,Y,XZ,YZ,X2,Y2. Radial Higher Order. Radial Full.
- Login as console and use “maintenance mode”.
- Single Deuterium signal, Homospoil or gradient. CDCl3, DMSO-D6, acetone-D6, C6D6 and D2O.
- Use Doped D2O or lineshape sample.
- Select “homospoil” method. D2O DMSO 4 scans 2 sec relaxation. Acetone 4 scans 6 sec relaxation. CDCl3 not a good choice as it is a weak solvent and require more scans.
- Tip angle 90°
- After completion select the data slate icon (green bottom right), Select range in the box mode. Connect X. Zoom in, exclude noise area. rescale vertical axis and get the percentage for the best shim area.
- Stack with profile (top hat) to check. (optional)
- Login as user Datum and perform “start Shimming” after entering the conditions obtained from above. Select “For this sample only and Preserve Shim Results.
- Do this for other solvents without Preserve Shim Results and Start Shimming.
- Check if gradient shim works in other user. System type. Uncheck “for this sample only” Set lower and upper range values.
- Solvents with more than one signal needs calibrate. Use Homospoil selective. It needs to have the soft pulse Lock Deuterium calibration done. 2H is deuterium. Works well with the no D shimming.
- Convection compensated shimming. Elevated temperature due to convection taking place. Fast_Homospoil_CC.
- Monitor gradient shimming profile. |X|. Use the profile to check for dirty tubes or sample defects.
- : 3D gradient shimming every 2 months.
After optimal shimming on a lineshape sample was achieved, save it as “system shims”. Login as console and use the maintenance mode to do gradient shimming calibration (do a shim map). Establish optimum shim range, (example 20% to 80%).
Update the each solvent shims. For single peak solvents CDCl3, Acetone, C6D6, etc use “Homospoil” and multiple peak solvents use “Homospoil Selective”
A presentation by Dr Paul Bowyer illustrating the concept of gradient shimming theory and practice.
Gradient shimming-Theory and Practice video