240 Programmed Temperature Vaporization Inlet (PTV)
Splitless modes
6 of 46
Jun 2001
Inlets
Agilent 6890 Gas Chromatograph Service Manual
Splitless modes
In splitless mode—with or without a pressure pulse—the solenoid valve is
closed during injection and vaporization of the sample and while the sample
transfers to the column. At a specified time after injection, the valve opens
to sweep vapors left in the liner out the split vent to prevent solvent tailing
due to the large inlet volume and small column flow rate.
Figure 240-3 shows the inlet flow control during injection and sample transfer
with the septum head installed. The flow sensor measures the flow rate, but
the pressure sensor on the septum purge line controls the column head
pressure using proportional valve 1.
In the septumless head, the flows are the same as in the septum head except
the septum purge vent is bypassed directly to the carrier flow through the
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