Address:
C. Eugene Bennett
Department of Chemistry
406 Clark Hall
Prospect Street
P.O. Box 6045
West Virginia University
Morgantown, WV 26506

Phone:
(304) 293-3435 X6439

Fax:
(304) 293-4904

Email:
Chemistry@mail.wvu.edu





Shimming On The Lock Signal

Shimming on the Lock Signal
Always retrieve a good starting shim set by typing rts(?stdshims?) load=?y? su. Adjust only z1 and z2 keeping in mind that they interact. For short samples (< 0.5 mL in volume or < 5 cm in height) adjustment of all axial shims (z1, z2, z3 and z4) must be done. Maximize the lock level with z1, and then maximize lock level with z1 and z2 (Fig. 1). Do this by making a change in z2 followed by maximizing with z1 gain. Continue to alternate in this manner until you can no longer increase the lock level. Then acquire your spectrum. When the sample is properly shimmed, the line will be symmetric. If not, the line will appear broadened. Look in the spectrum for the solvent signal (CDCl3, TMS, or any single line in the spectrum). If they do not have splitting (or shoulders), it means that you have a good line shape. You can then save the satisfactory shims (for that particular solvent) by typing svs(?name?). For short samples you need to adjust z1-z4 as mentioned above. To do this first maximize lock level with z1 and z3 then with z1 and z2; secondly maximize lock level with z2 and z4 and then with z1 and z2.
When you have adjusted the lock level to a maximum, click the Close button on the top of the window. The next step will be acquiring your spectrum.

(2a) - Lock off
(2b) - Lock off
(2c) - Lock off
(2d) - Lock off
(2e) - Lock off
(2f) - Lock off
(2g) - Lock on
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