About Makeup Gas - Agilent Technologies 7890 Series Advanced Operation Manual

5
Detectors

About Makeup Gas

168
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].
3
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