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03-914648-00:7
Constant
Column
Flow
Type 1 EFC with the CP-1079 will automatically building a
pressure program to keep the column flow rate constant
during temperature programming of the column oven when
Constant Flow is selected. Constant Flow is enabled on
page 2 of the EFC method section. The same general
guidelines should be followed for all injection modes. If the
column is operated isothermally then the pressure should be
kept constant. If the column is temperature programmed
then the pressure can either be held constant or
programmed. Programming the injector pressure generally
has no significant impact on chromatography, other than a
slight reduction in analysis time. In some instances
resolution may either improve or degrade depending on the
settings. For larger volume hot splitless injections, a
technique called Pressure Pulse is also available for use
with Constant Flow programs with Type 1 EFC. Use the
following guide for setting injector pressure and/or building a
pressure program.
Temperature programming the column oven results in an
increase in carrier gas viscosity which results in a decrease
in column flow rate. This effect can be offset by applying the
appropriate column pressure program. The second page of
the TYPE 1 EFC allows constant flow mode to be selected.
If Constant Flow Programming is enabled, a pressure
program based on the column parameters and the column
oven temperature program will be automatically built
whenever the method is activated. If the desired column 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.
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