Mmi Direct Mode - Agilent Technologies 7890 Series Advanced Operation Manual

3
Inlets

MMI Direct Mode

78
If desired, turn Gas saver on. Make certain the time is set
6
after the Purge time.
Press [Prep Run] (see
7
before manually injecting a sample.
If the column is not defined
1 Set up the parameters as described for the defined
column case.
Set Total flow greater than the column flow plus the
2
septum purge flow to guarantee adequate column flow.
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.
"Pre Run and Prep Run"
Advanced Operation Manual
on page 40)