About Makeup Gas - Agilent Technologies 7820A Advanced User's Manual

5
Detectors

About Makeup Gas

66
Most detectors use a makeup gas to increase the flow rate
through the detector body. This sweeps peaks out of the
detector quickly, avoiding mixing of components and loss of
resolution. This is particularly important with capillary
columns because the column flow rates are so small.
The makeup gas line of your detector parameter list changes
depending on your instrument configuration.
If you have an inlet with the column not defined, the makeup
flow is constant. If you are operating with column defined, you
have a choice of two makeup gas modes.
Constant makeup This mode provides a constant flow of
makeup gas to the detector.
Column + makeup = constant This mode provides a variable
flow of makeup gas to the detector. As column flow increases or
decreases, the makeup flow changes to provide a constant
combined flow to the detector. If you choose this option, enter a
value under Combined flow. The Combined flow line always
displays the same value, while the Makeup line changes as the
actual makeup flow changes.
To change the makeup gas flow mode
Press [Front Det] or [Back Det].
1
Scroll to Mode. Press [Mode/Type].
2
Scroll to the correct mode and press [Enter].
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