Section 4: Experimental Tutorials
4.1 Water-Water Baselines
The following experimental tutorial is designed to acquaint the new user with the basic features
of both the hardware and software of the VP-ITC instrument, as well as to provide experience
with several manipulations that must be mastered in order to get the highest quality data from
your instrument. Rather than beginning experimentation on the VP-ITC using precious biological
samples, we strongly suggest that each user of the VP-ITC instrument complete the following
tutorials first.
The recommended procedures for preparation of solutions, degassing, filling the cell and injection
syringe, etc. have already been discussed in the previous sections, while conducting the following
tutorials you may want to refer to these sections for more detail.
Power Up the System
Power up the Computer Controller and VP-ITC, doing the following steps in order.
1.
Turn on the computer controller. The VP-ITC power switch must be off.
2.
Once the computer controller is on and Windows is running, turn on the power
switch at the rear of the VP-ITC.
3.
Launch the VPViewer application by double clicking its icon on
the Windows desktop or from the Windows taskbar by selecting
Start : Programs : MicroCal’s VPITC : VPViewer ITC.
Degas Samples
Begin by degassing (with stirring) ca. 40 ml of distilled water for ca. 5 minutes using your
ThermoVac (see page 40 for more information), or suitable substitute. This degassed water will
be the solution that will go into the sample cell, reference cell and syringe.
Fill the Cells
Load the 2.5ml glass filling syringe with water, and while holding the syringe
vertically, tap the syringe bottom after loading so all bubbles float to the top surface.
Enter the needle into the sample cell entry tube (this is the center hole located to the
right of the reference entry hole) and carefully slide the needle down the tube until it
just touches the bottom of the cell. Lift the syringe so that the needle end is just off
bottom (about 1 mm), then slowly depress the plunger so that the cell fills from the bottom up.
After ca. 1.8 ml of the degassed water has been entered, you will be able to see the water come to
the top of the small entry tube. Once you see the liquid level rise above the top of the access
tube, depress the plunger very quickly 1-3 times to deliver abrupt bursts of ca. 0.25 ml. The
purpose of these last bursts is to dislodge any bubbles, which might be clinging where the entry
tube joins the cell.
Refer to page
for more
information
If the reference cell has not previously been filled with degassed water, then carry out the same
procedure to fill it. There is no need to refill the reference cell with each experiment, A water
reference may be good for a week or two with no attention, if the water was thoroughly degassed
before filling. To prevent sample overflow into the reference cell, a reference plug and insertion
device has been provided to cap the reference cell access tube after filling.
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