Heating The Mmi; Cooling The Mmi - Agilent Technologies 7890 Series Advanced Operation Manual

3
Inlets

Heating the MMI

Cooling the MMI

56
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.
If using a Merlin Microseal™ septum, finger tighten the
septum nut, until snug (not loose). The pressure capacity
depends on the duckbill seal used.
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
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.
If using cryogen to cool the MMI inlet, both liquid carbon
dioxide (LCO ) and liquid nitrogen (LN
2
addition to the cryogenic coolants, the MMI supports
compressed air cooling on both the LCO
options for legacy applications.
"MMI split and pulsed split
) are supported. In
2
and LN
2
Advanced Operation Manual
modes"
cooling
2