5 Operating in EI Mode
Controlling Column Flow
5977B Series MSD Operating Manual 115
Controlling Column Flow
Carrier gas flow is controlled by inlet pressure in the GC. Set the column mode to
Constant Pressure to maintain a constant inlet pressure, and the column flow
will decrease as the GC oven temperature increases. With EPC and the column
mode set to Constant Flow, the same column flow is maintained regardless of
temperature.
The MSD can be used to measure actual column flow. You inject a small amount
of air or other unretained chemical, and time how long it takes to reach the MSD.
With this time measurement, you can calculate the column flow. (See “To
Calibrate Column Flow Linear Velocity in a 7890 GC” on page 95 as appropriate.
For an 8890 GC, see the 8890 GC Operating Manual.)
Controlling JetClean Hydrogen Flow
The JetClean option uses hydrogen gas for cleaning the ion source. The
JetClean system MFC sends hydrogen to the to the analyzer through the CI line
in the GC/MSD interface. The flow rate is controlled by the MassHunter GC/MS
Acquisition software. The JetClean system is only supported on turbo based
systems using an EI Inert source, or an EI HES. (See “To Set the Operation Mode
for the Optional JetClean System” on page 129.)
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