VT
Operation on Burger
Instructions depend
on your desired sample temperature. Select the appropriate instruction set below.
Instructions for temperatures < 20oC
Instructions for temperatures > 20oC
Instructions
for temperatures < 20oC
Use nitrogen
if you wish to collect spectra below 20oC. A gas bottle will last about
3 hours. A 240 liter dewar of liquid nitrogen will last 2-4 days.
Connect the regulator with
the red ring at the output hole to the nitrogen tank.
Log on to burger and eject
the sample. When the sample has been removed from the spectrometer and the ejection
air turned off go to the stack of three gauges on the wall to the left of the
magnet. Turn the top valve (which has a nylon tube in it and has an output pressure
of ~25 psi) off. Remove the hose from the green nozzle. You should push the green
ring in a tiny bit and pull the hose out of the ring.
Connect the hose to the red
nozzle on the tank regulator by inserting the hose into the red nozzle and pushing
it as far into the nozzle as possible.
Open the use valve on the tank
and then open the regulator. Adjust the output pressure on the regulator so that
it is ~30 psi. You may need to turn on the pressure builder if one is present.
You should hear air flowing through the machine. Insert your sample.
Go to the console and type
the following: sethw('vt','reset') You should make sure the VT light next
to the LED readout on the console to the left of the monitor is not blinking.
Enter the following: vtc=25
"vtc" stands for Variable Temperature Cutoff. When the working temperature is
above the vtc value, the VT gas bypasses the cooling coil. When the working temperature
is below the vtc value, the VT air passes through the cooling coil.
Enter temp=20 su
and this will set the VT temperature to 20oC. Since you set the vtc
value to 25, this command will initiate VT air flow through the cooling coil.
Let the nitrogen flow for ~5-10 minutes to get all of the air out of the probe.
NOTE: The normal probe used
for standard proton/carbon data is good to -20oC. If you need to work
below -20oC, talk to Dr. Ellena a few days before you have instrument
time so that he can change the probe.
Put a dewar (should be in the
room) under the VT coil and raise it on a lab jack (also should be in the room).
Fill the dewar with either dry ice/isopropanol (-78oC, recommended
for work to -20oC or higher) or liquid nitrogen.
NOTE: Be careful to fill
the dewar so that the coolant level is barely above the coil. Filling it higher
(especially with liquid nitrogen) can cause the area above the coil to freeze
and consequently VT gas flow to the probe may slow or stop.
Go back to the console and
type temp=X su where X is your working temperature. Allow the machine to
cool down to your temperature (this should be fairly rapid), then tune the probe,
shim and run your experiments. If you will be using Glide or loading parameters
after temperature equilibration see the instructions
below.
When you are done with your
VT experiments, type temp=20 su to let the spectrometer change the sample
temperature to 20oC. Remove the dewar from underneath the coil (it's
probably a good idea to use thermally insulated gloves for this). Get a hair dryer
or heat gun and warm the coil up until it doesn't feel cold anymore.
Go to the console and type
temp='n' su. This will turn the VT off. Let the nitrogen flow through the
coil until the probe temperature remains above 15oC.
Eject your sample and turn
the nitrogen from the tank off. Remove the hose from the regulator and connect
it to the top of the three valves on the left wall facing the magnet (the valve
from which you originally got the hose). Open the nozzle on so that the output
pressure is 25 psi.
Put the standard in the magnet,
lock it and log off.
Pat yourself on the back for
a job well done.
Instructions
for temperatures > 20oC
Air can be used
as the VT gas for temperatures > 20oC. Enter vtc=20 temp=x
su
where x is the desired temperature value in oC. Wait 5-10
minutes for temperature equilibration. If you will be using Glide or loading
parameters after temperature equilibration see the instructions
below.
When your high temperature work has been completed enter temp='n' su,
this will turn the VT off.
Using
Glide or loading parameters
after temperature equilibration
Proton and carbon
data that need to be acquired at your working temperature can be acquired with
no problem. After loading the standard parameters and before entering su,
if the sample temperature is < 20oC enter vtc=25 and temp=x;
if the sample temperature is > 20oC enter vtc=20 and temp=x.
The preceeding is necessary because the standard proton and carbon parameters
will turn the VT off.
If you need to run 2D spectra (ie. gHSQC, NOESY or COSY) at variable temperature,
you need to change some things since the 2D experiments (via GLIDE) read a standard
file in which the VT is off:
Go to the vnmrsys/
folder and then go to the stdpar/ folder. Click on the H1.par
file and then click Load. This will load the standard parameters file
which GLIDE uses for 2D acquisitions. Under in the gray table below the spectral
window, one line will say "temp." Across from this will be a line saying "not
used." Type the following:
temp=x <enter>
svp <enter>
When the computer prompts
you to input a filename for the file, enter H1. The computer will ask
you if you wish to save over the old file. Click <enter>, which
is default for "okay." Now if you run anything through GLIDE, it will use the
temperature you set in the H1.par file.
REMEMBER TO SET THE TEMPERATURE
BACK TO NORMAL BEFORE YOU LOG OFF!!!!!!!!
To do this, load the H1.par
file as described above. Type the following:
temp='n' <enter>
svp <enter>
and replace the H1 file as
described above.
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Instructions