I have 13 replies to my post and it is almost unanimous that gradient shims
works well with automation. Some gave excellent practical hints which are
what makes this usergroup so useful. Thanks to all of you.
Here is the concise summary.
1. Gradient shims works well for solvents with single strong deuterium
peak. Shim time is between 30 sec - 2 min. Solvents like CDCl3, CD3OD takes
more time and also proper setup.
2. Gradient shims are sensitive to temperature changes. Hence, the
sample must be equilibrated to the correct temperature inside probe before
shimming. This time delay is very important to achieve proper peak shapes
each time. Test the proper delay time necessary for your probe. With this
added time, gradient shims can take a total of 3 to 5 minutes for each
sample.
3. Gradient shims consistently take the same time and give the same
quality. Failure rate is much low compared to simplex shim method.
4. There is no difference in quality of shims or time required for
shimming between homospoil & gradient amplifier.
5. Main advantage of gradients in fast 2D data acquisition with
excellent S/N is well worth the upgrade. It is far more important than
shimming.
Dr. Gopal Subramaniam
Dept. of Chemistry & Biochemistry
Queens College, CUNY
Flushing, NY 11367
Received on Tue May 24 2005 - 16:50:01 MST