VP-ITC MicroCalorimeter User’s Manual
PreRun Thermostat
Once the cells and jacket have reached the starting temperature, the ITC will enter the 2
nd
prerun
state, the
Prerun Thermostat
state. The purpose of the PreRun Thermostat state is to maintain the
starting temperature, for the requested period of time. This will allow time for thermal gradients
within the ITC cell thermal core, to minimize before the experiment starts to reduce their affect
during the experiment. The duration of the PreRun Thermostat state is 5 minutes.
PreStirring Equilbration
After the pre-run thermostat period has elapsed, VPViewer and the ITC cell will enter PreStirring
equilibration. During this state the instrument will establish a zero degree DeltaT (temperature
difference between the jacket and the cells) to establish adiabatic conditions suitable for sensitive
thermal measurements. The DP signal will stabilize at a power level that is close (i.e within 1
µcal/sec) to the ‘Reference Power’ setting.
Final Baseline Equilibration
After the PreStirring Equilibration has been reached, the VP ITC instrument will enter the Final
Baseline Equilibration or the stirring state. The VP will start rotating the syringe. The start of the
stirring will cause the DP signal will deflect downward, then the signal will increase, but stabilize
at a level slightly lower than the non-stirring baseline. The instrument will stir continuously for
the remaining portion of the run.
Running
Once the DP signal has stabilized after the start of the stirring, the instrument will enter the run
state. The run commences with an initial delay to provide baseline data prior to the first injection.
Then the injections will be executed according to the injection schedule.
The instrument responds to an exothermic reaction by decreasing the feed back heat provided to
the sample cell. That is, heat added to the sample cell by an exothermic reaction will result in a
downward deflection in the baseline DP signal. This downward deflection is proportional to the
energy not needed to maintain the temperature equilibrium between the sample and reference
cells. The integrated area of this deflection is referenced to the baseline before the injection and
after the reaction has completed. An endothermic reaction will require more heat in the feed back
loop to maintain the same temperature resulting in a positive deflection.
Origin Main Menus
A description of the features of these menu items may be found in the Origin User’s Manuals.
These features are generally not utilized during data collection.
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