User guide

228 Advanced User Guide
8 Inlets
• Downward programming can be used to prepare the inlet for
the next run. This can reduce cycle time for greater sample
throughput.
Cooling the PTV inlet
If cryo is turned on, and if the inlet is cooled during a run,
cryogen is used to achieve the setpoint. This may have a
negative impact on the chromatographic performance of the
oven and cause distorted peaks.
The sample may be injected into either a cooled or heated inlet.
The initial inlet temperature can be reduced to –60 °C (with
CO
2
cooling) or to –160 °C (with liquid N
2
cooling).
The inlet uses the same coolant as configured for the oven.
PTV inlet split and pulsed split modes
The two split modes—with or without a pressure pulse—divide
the gas stream entering the inlet between the column flow, the
split vent flow through the solenoid valve, and the septum purge
flow. The ratio of the split vent flow to the column flow is called
the split ratio.
The next figure shows the flows with the septum head. Flows
with the septumless head are the same except that the septum
purge flow bypasses the head.