Section 3: Running an ITC Experiment
boiling the sample in the chamber you should adjust the adjusting knob of the bleeder valve
counterclockwise to reduce the vacuum. Any customers with a ThermoVac that does not include
this option may request one through our sales department.
To degas solutions before placing into the cells or injection syringe, please do the following.
•
Turn on the Power Main Switch.
•
Set the desired temperature for the solution.
•
Place your solution to be degassed into a test tube, add a small stir bar and place the tube into
one of the open cylinders of the Tube Holder insert.
Please Note
: To conserve titrant sample for loading into the injection syringe, use the small
test tubes provided with the ThermoVac.
If you wish to use a tube or beaker larger than will fit into the Tube Holder you may remove
the Tube Holder by simply lifting it up. Due to the tight fit of the Tube Holder, it may be
difficult to lift the Tube Holder out of the sample chamber, in this case you may use a 3/32”
hex (Allen Key) wrench to turn a screw , located at the bottom of the center hole of the Tube
Holder, to lift the Tube Holder out.
•
Turn the stirring on.
•
Turn on the vacuum. Push the switch to the right to activate the vacuum for a preset (ca
.
5
minutes) duration. Push the switch to the left if you wish to manually control the time for the
vacuum. If excessive bubbling occurs that could boil over your sample you may adjust the
bleeder valve. Turning the adjusting knob clock wise will increase the vacuum while a
counterclockwise turn will decrease the vacuum strength.
•
Place the Vacuum cap on top of the sealing o’ring. The sound of the vacuum pump will
change pitch to indicate the vacuum has sealed the Cap to the o’ring. Once the vacuum has
sealed, the Vacuum Cap will be held firmly in place, till the vacuum pump shuts off.
Please Note
: Once the vacuum pump has been turned off, the vacuum in the sample
degassing chamber may be released at any time causing the Vacuum Cap to fall off the
sealing o’ring. Make sure that there is nothing on top or next to the ThermoVac that may
spill or break due to the sudden movement of the Vacuum Cap.
For the first 30 seconds after the vacuum pump is turned off, the vacuum in the sample degassing
chamber may remain fairly tight making the removal of the Vacuum Cap difficult. During this
period, the easiest way to release the vacuum is to open the bleeder valve by turning the adjusting
knob counter-clockwise.
3.3 Cell Loading
The cells are filled using the long needled 2.5 ml glass syringe, by filling from the bottom of the
cell to the top. The tops of the access tubes are visible within the cell port. The sample cell is in
the center and the reference is offset to the left, as viewed from the front of the instrument.
•
Degas the sample, as described in the previous section.
•
Slowly draw a minimum of 1.8 mL of solution into the filling syringe. (It may be
advantageous to fill using more solution, but after filling, you should remove all but the 1.8
mL that is in the cell and access tube).
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