Agilent Technologies G7035A, Operation Manual, Page: 117 / 172

Operating in Chemical Ionization (CI) Mode
4
5977 Series MSD Operation Manual 117
To Monitor CI Mode High Vacuum Pressure
Procedure
1
Start up and pump down the MSD. See “To Pump Down the MSD in CI
Mode” on page 98.
2
In the
Tune and Vacuum Control
view select
Turn Vacuum Gauge on/off
from the
Vacuum
menu.
3
In the
Instrument Control
view you can set up an MS Monitor for reading. The
vacuum can also be read on the LCP or from the Manual Tune screen.
The gauge controller will not turn on if the pressure in the MSD is above
approximately 8
× 10
-3
Torr. The gauge controller is calibrated for nitrogen, but
all pressures listed in this manual are for helium.
The largest influence on operating pressure is the carrier gas (column) flow.
Table 20 on page 118 lists typical pressures for various helium carrier gas
flows. These pressures are approximate and vary from instrument to
instrument.
Typical pressure readings
Use the G3397B Micro-Ion vacuum gauge. Note that the mass flow controller is
calibrated for methane and the vacuum gauge is calibrated for nitrogen, so
these measurements are not accurate, but are intended as a guide to typical
observed readings (See
Table 20 on page 118). They were taken with the
following set of conditions. Note that these are typical PCI temperatures:
WA R N I N G
If you are using hydrogen as a carrier gas, do not turn on the Micro-Ion vacuum
gauge if there is any possibility that hydrogen has accumulated in the manifold.
Read
“Hydrogen Safety” on page 19 before operating the MSD with hydrogen
carrier gas.
Source temperature 250 °C
Quad temperature 150 °C
Interface temperature 280 °C
Helium carrier gas flow 1 mL/min