User guide

186 Advanced User Guide
8 Inlets
About the Multimode Inlet
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. Both the split vent valve and
the septum purge valve are 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 “MMI solvent vent mode”
on page 201.
Septum tightening (MMI)
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.
With higher inlet pressures, tighten the septum retainer until
the C- ring stops turning, indicating that the retainer is in firm
contact with the septum.
1 mm