Splitless Mode - Agilent Technologies 6890 Series Service Manual

Gas chromatograph

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Split/Splitless Inlet

split ratio remains constant due to electronic control. The actual flow rate

through the inlet is much higher during the injection period, transferring the

analytes quickly onto the column which minimizes sample losses that can

occur in glass inlet liners. After the pulsed time expires, the split flow and

column flow are returned to the lower flows selected for best chromatography.

Splitless mode

For an EPC inlet during splitless injections, PV1 is used to control the inlet

pressure as measured by PS. V is an on/off valve which is turned off so there

is no flow out of the split vent. PV2 is turned on at a nominal value so that

there is no back pressure on V. FS will still be measuring flow, but it is no

longer used to control PV1. In this configuration, the total flow into the inlet

is the column flow + septum purge flow. At the user specified purge time, the

inlet control is returned to split mode (see Figure 210-1 ) to allow the inlet to

Agilent 6890 Gas Chromatograph Service Manual

6890a 6890 plus