Operating in Chemical Ionization (CI) Mode 4
5977 Series MSD Operation Manual 91
The CI GC/MSD Interface
The CI GC/MSD interface (Figure 15 on page 92) is a heated conduit into the
MSD for the capillary column. It is bolted onto the right side of the analyzer
chamber, with an O-ring seal and has a protective cover, which should be left
in place.
One end of the interface passes through the side of the GC and extends into
the oven. It is threaded to allow connection of the column with a nut and
ferrule. The other end of the interface fits into the ion source. The last 1 to
2 mm of the capillary column extend past the end of the guide tube and into
the ionization chamber.
Reagent gas is plumbed into the interface. The tip of the interface assembly
extends into the ionization chamber. A spring-loaded seal keeps reagent gases
from leaking out of the CI ion source at the tip. The reagent gas enters the
interface body and mixes with carrier gas and sample in the ion source.
The GC/MSD interface is heated by an electric cartridge heater. Normally, the
heater is powered and controlled by Thermal Aux #2 heated zone of the GC.
The interface temperature can be set from MassHunter Data Acquisition or
from the gas chromatograph. A sensor (thermocouple) in the interface
monitors the temperature.
This interface is also used for EI operation in CI MSDs. The CI tip seal,
necessary for CI operation, can stay in place when the EI extractor ion source
is in use. It is easily replaced for the standard or inert EI ion source.
The interface should be operated in the 250 to 350 C range. Subject to that
restriction, the interface temperature should be slightly higher than the
maximum GC oven temperature, but never higher than the maximum column
temperature.
CAUTION
Never exceed the maximum column temperature, either in the GC/MSD interface, the
GC oven, or the inlet.
WARNING
The GC/MSD interface operates at high temperatures. If you touch it when it is hot,
it will burn you.
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