Frequently Asked Questions (FAQ)
Z33085_2_002 31
Frequently Asked Questions
(FAQ)
The lock procedure works well with the solvent, but not with the frequency lock.
1. The wrong solvent has been selected and thus the frequency of the compound used for
the NMR Thermometer is out of range.
2. The concentration of the compound used for the NMR Thermometer is too low. Please
check table 1 and 2 which give typical concentrations required.
3. The lock power for the thermometer compound is too high or too low. Change the value
“Temperature Lock power” in the edlock table and repeat the lock procedure. The value of
the temperature lock power typically is a few dB lower than for the field lock power.
4. The chemical shift of the compound used for the NMR Thermometer is too closed to the
chemical shift of the solvent. Here it can happen that the lock procedure for both, the field
and the frequency lock, is working fine on a 700 MHz spectrometer, while it fails on a
lower field spectrometer due to the reduced shift difference (in Hz) at a lower field. In that
case a different thermometer compound has to be used.
The lock procedure worked well for field and frequency lock, but the temperature regulation of
the NMR Thermometer is instable.
• The lock power for the thermometer compound is too high. Reduce the value
“Temperature Lock power” in the edlock table and repeat the lock procedure. The value
for the temperature power typically is a few dB lower than for the field lock power.
Does the NMR Thermometer work when experiments with pulsed field gradients are
performed?
• Yes, like the field lock the NMR Thermometer can be used together with pulsed field
gradients. Both, the field and the frequency lock regulation are triggered with lock hold
commands of the pulse program. Lock hold commands are standard in all standard pulse
programs using pulsed field gradients.
After enabling the NMR Thermometer the temperature starts to increase/decrease or during
an experiment with RF heating (see above) temperature is decreasing?
• The chemical shift – temperature values in the edlock table for the particular solvent are
probably wrong for instance after creating an .xml file and using a positive sign for the
slope instead of a negative one.
7
To Next Page
Loading...
Need help?
General
