User guide

Inlets 8
Advanced User Guide 209
If the column is not defined
1 Set up the parameters as described for the defined column
case.
2 Set Tot a l f l ow greater than the column flow plus the septum
purge flow to guarantee adequate column flow.
MMI Direct Mode
MMI Direct Mode is a pneumatic configuration that allows
on- column like behavior. In this mode, you still use a liner to
trap involatile material but the sample can only enter the
column.
Direct mode works best with direct connect liners. These liners
form a seal with the column so that the sample cannot leak out
of the liner. The inlet is held at a temperature below the solvent
boiling point, just as in cool on- column (COC) during the
injection. Pneumatically, the inlet is in forward pressure
regulation, similar to the splitless portion of splitless mode. The
inlet is then temperature programmed to transfer any
remaining volatile material to the column.
The only control parameter for Direct Mode is inlet pressure.
You can run the column in any of its normal control modes
(constant pressure, constant flow, ramped pressure, ramped
flow). Gas saver does not work in this mode as there is no purge
state.
The next figure shows the flows with direct mode.