User guide

Inlets 8
Advanced User Guide 187
If using a Merlin Microseal™ septum, finger tighten the septum
nut, until snug (not loose). The pressure capacity depends on
the duckbill seal used.
Heating the MMI
Programming the MMI temperature is similar to programming
the column oven. Access the inlet parameters by pressing [Front
Inlet] or [Back Inlet]. Temperature can be programmed with an
initial temperature and up to 10 ramps (rates and plateaus). See
“MMI split and pulsed split modes” on page 191 for details.
At the end of the run and during post- run, the MMI is held at its
final temperature. This permits backflushing without
contaminating the inlet.
Additional temperature ramps
For most purposes, the MMI is designed to hold the sample in
the inlet liner until the entire sample—there could be several
injections—has been injected. Then the MMI is heated rapidly to
transfer the sample to the column. This can be accomplished
with an initial hold, a single ramp, and a hold at the end to
complete sample transfer.
Additional ramps are available and have several possible uses:
• The inlet can be heated to a high temperature to thermally
clean the liner for the next run.
• The inlet can be programmed downward—just set the Final
temp below the previous temperature—to reduce thermal
stress on the inlet.
• Downward programming can be used to prepare the inlet for
the next run. This can reduce cycle time for greater sample
throughput.
Cooling the MMI
If using cryogen to cool the MMI inlet, both liquid carbon
dioxide (LCO
2
) and liquid nitrogen (LN
2
) are supported. In
addition to the cryogenic coolants, the MMI supports
compressed air cooling on both the LCO
2
and LN
2
cooling
options for legacy applications.
If using cryo as the coolant when configuring the initial inlet
setpoint, set the Use cryo temperature equal to or higher than the
inlet setpoint to cool the inlet and hold the setpoint until the