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11.6 Gradient Shimming
The deuterium parameters are saved for future use when the shimmap is saved, and are used
the next time gradient autoshimming is run.
Table 55. Deuterium Parameters
Solvent
nt
d1 (sec)
Gain
Inova
Mercury
deuterochloroform
8-32
3
36
18
dmso-d6
4-16
3
28
10
D2O
1-4
3
24
6
deuterobenzene
1-4
3
24
6
deuteroacetone
1-4
6-12
24
6
Note: Actual parameters might vary, depending on solvent concentration, probe, and
system hardware.
Homospoil Gradient Shimming for 1H or 2H
It is also possible to use the Z1 room temperature shim as a homospoil gradient, instead of
using a pulsed field gradient or PFG. Use of this option is recommended only if a PFG
amplifier or probe is not available. For details on how to configure a homospoil gradient,
see the section “Homospoil Gradient Type” in the chapter on PFG modules operation in the
manual User Guide: Liquids NMR. The system administrator must make a shimmap using
homospoil before homospoil gradient shimming can be used. Follow the procedure in
“Mapping the Shims,” on page 375.
At step 4 select tn as appropriate, set tof on resonance, and then find the 90° pulse. If
deuterium is used, tpwr should be kept low, with a 90° pulse greater than about 200 µs.
At step 6, select either Homospoil H1 for proton parameters or Homospoil H2 for
deuterium parameters, as appropriate. Homospoil gradients must be configured at this step
(use config or set gradtype='nnh').
At step 7, further testing of the gradient shimming parameters for homospoil can be done
as follows:
1.
Enter gmapsys, and click on Set Params > Go,dssh.
2.
Using the 90° pulse from step 4, calibrate the 90° and 180° pulses to obtain an echo.
Enter df to display the FID. You should see an echo forming in the middle of the
FID.
3.
If needed, adjust sw so that the gradient covers at least 10% of the spectral window.
Increase np to 512 to improve Hz/point resolution. However, np should be adjusted
so that at is not longer than the homospoil time limit (20 ms on standard UNITYINOVA
and UNITYplus and 200 ms with the automated deuterium gradient shimming
module). The acquisition time (at) should also be shorter than T2. Set d2=at/4.
Once all the parameters are set, click on Automake Shimmap (step 8). The parameters are
saved when the shimmap is done and are used the next time gradient autoshimming is run.
To use homospoil deuterium gradient shimming with different solvents, set the parameter
gmap_findtof='y'. This should be done before making the shimmap, or may be set in
the corresponding parameter set in gshimlib/shimmaps. Gradient shimming will then
perform a calibration to find tof before autoshimming starts. This takes an extra iteration in
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