VT on Agilent NMR
# Under low temperature, use Nitrogen gas (instead of air).
# Transfer line, especially the glass mouse, is fragile. Be cautious when use it.
# Manually insert the sample in the magnet first.
# The VT and running NMR are separated. Change the VT first. After the temperature reaches the target, start running NMR.
(A) VT availabilities
Machine VT range
A500a minus 80 to plus 130
A400b minus 80 to plus 130
A500b minus 10 to plus 130
(B) For high temperature:
1. In Vnmrj, go to “Start” -> “Spin/Temp” -> Enter the target temperature (entering number and hit return! The mark should change position) -> hit “Regulate temp”. When the temperature is close to the target, the change will be slower.
2. If the temperature does not increase, hit “Reset pneumatic router” and “Reset VT controller”, until the VT works.
3. After temperature is stabilized, run the NMR as usual.
(C) For low temperature:
1. Insert the exchange coil of the transfer line into a dewar. Connect the transfer line to the probe.
2 . Check the gas source is N2. Otherwise change it to N2 gas.
3. In Vnmrj, go to “Start” -> “Spin/Temp” -> set a target temperature 5 degree higher than room temperature, and hit “Regulate temp”. If the temperature does not increase, hit “Reset pneumatic router” and “Reset VT controller”, until the VT works.
4. Pour liquid nitrogen into the dewar.
5. Enter the target temperature and hit “Regulate temp” again.
6. When the temperature is stabilized, run the NMR as usual.
7. After the experiment finishes,
a. Set target temperature back to 25 C and hit “Regulate temp”.
b. Disconnect the ‘Transfer line’.
c. Warm the ‘Transfer line’ with air.
d. Put D2O sample into magnet when the temperature reaches above 0 degree.
(D) Temperature calibration
For exact determination of sample temperature when using the VT unit,
a temperature calibration is needed.
Samples of ethylene glycol are used for high- temperature calibration
( > 295 C), and samples of methanol are used for low- temperature calibration (< 300 C).
Put sample into the magnet, and get a simple proton spectrum. Align two cursors on the two resonants in the spectrum, then enter tempcal(‘e’) for ethylene glycol, or enter tempcal(‘m’) for methanol. The temperature is calculated based on the difference frequency between the cursors.