About The Multimode Inlet; Septum Tightening (Mmi) - Agilent Technologies 7890 Series Advanced Operation Manual

About the Multimode Inlet

Septum tightening (MMI)

Advanced Operation Manual
The Agilent Multimode (MMI) Inlet System has five operating
modes:
• The split mode is generally used for major component
analyses.
• The pulsed split mode is like the split mode, but with a
pressure pulse applied to the inlet during sample
introduction to speed the transfer of material to the
column.
• The splitless mode is used for trace analyses.
• The pulsed splitless mode allows for a pressure pulse
during sample introduction.
• The solvent vent mode is used for large volume injection.
Either single or multiple injections can be made for each
run.
• The direct mode allows for a direct forward pressure of
carrier gas through the column. The split vent valve is
closed.
The MMI can be used with both manual and automatic
injection.
Automatic multiple injections (large volume injections) is not
available under GC control alone. See
mode" on page 70.
Septum retainer nuts must be tightened enough to obtain a
good gas seal, but not so much as to compress the septum
and make it difficult to push a syringe needle through it.
For the standard septum retainer nut, an internal spring in
the septum retainer applies pressure to the septum. For inlet
pressures up to 100 psi, tighten the retainer until the C- ring
lifts about 1 mm above the top surface. This is adequate for
most situations.
Inlets
"MMI solvent vent
1 mm
3
55