Pumping Down; Controlling Temperatures; Controlling Column Flow - Agilent Technologies 5975T LTM GC Operation Manual

Pumping Down

The data system or local control panel helps you pump down the MSD. The
process is mostly automated. Once you close the vent valve and turn on the
main power switch (while pressing on the sideplate), the MSD pumps down by
itself. The data system software monitors and displays system status during
pumpdown. When the pressure is low enough, the program turns on the ion
source and mass filter heaters and prompts you to turn on the GC/MSD
interface heater. The MSD will shut down if it cannot pump down correctly.
Using the menus or MS monitors, the data system can display the motor speed
for turbo pump MSDs (percent spin speed).
The LCP can also display this data.
If you are using hydrogen as a carrier gas, do not turn on the Micro-Ion vacuum
WA R N I N G
gauge if there is any possibility that hydrogen has accumulated in the analyzer
chamber. Read
gas. Pump down for 25 minutes before you turn on the vacuumgauge.

Controlling Temperatures

MSD temperatures are controlled through the data system. The MSD has
independent heaters and temperature sensors for the ion source and
quadrupole mass filter. You can adjust the setpoints and view these
temperatures from the data system or from the local control panel.
The GC/MSD interface temperature can be set and monitored from the data
system.

Controlling Column Flow

Carrier gas flow is controlled by head pressure in the GC inlet. For a given
head pressure, column flow will decrease as the LTM column temperature
increases. With electronic pneumatic control (EPC) and the column mode set
to Constant Flow, the same column flow is maintained regardless of
temperature.
5975T LTM GC/MSD Operation Manual
"Hydrogen Safety" before operating the MSD with hydrogen carrier
Operating in Electron Impact (EI) Mode
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