CP-3800 GC Operator’s Manual
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flow or the column oven temperature program is changed, the method must
be reactivated to derive a new pressure program for these new conditions.
When entering a pressure program to maintain constant column flow rate,
the program is based on the column temperature program. If the column
oven is operated isothermally, then constant pressure is maintained to
achieve a desired flow rate.
Pressure Pulse
Once you have selected Constant Flow programming, a softkey will be
displayed on the second page of the Type 1 EFC section. This softkey is
labeled Pressure Pulse. Selecting Pressure Pulse will give you the option of
enabling a pressure pulse, setting the desired pressure, and the duration for
which the pressure should last. Typically, the pressure pulse pressure will be
held for between 30 and 90 seconds. The purpose of the pressure pulse is
two fold. The higher pressure will prevent the solvent vapor cloud from
becoming excessively large allowing larger injection volumes and providing
more efficient passage of the sample into the column. The higher pressure
also causes higher flow rates into the column making the transfer quicker
and thus preventing excessive residence times in the injector with
consequent decomposition of labile compounds.
If you elect to use
Pressure Pulse technique you will need to perform septa purge
calibration using the higher pressure pulse pressure.
•
First the GC will go Ready based on the calculated constant flow
conditions.
•
Once the initial Ready conditions are achieved, the pressure pulse
pressure will be applied to the system.
•
When the Pressure Pulse pressure has been achieved, the GC will go
to Ready and, if an autosampler is connected, the autosampler will
begin sampling in preparation for injections; if you are performing
manual injections, you may inject your sample as soon as the Ready
LED turns green.
Gas Saver
For type 1 EFC a specific Gas Saver Flow and a timeout period may be set.
A time entry of 0 turns the Gas Saver feature off
. If a non-zero time is
entered, the Gas Saver timer will start incrementing upon a method
activation. If a run is not started or another method not activated before the
timer expires, the set Gas Saver flow rate will be started. A message will be
logged in the instrument log.
The fault is cleared by activating a method.
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