Direct Mode - Agilent Technologies 6890 Series Service Manual

250 Volatiles Interface
Theory of operation
Total flow
control loop
Supply
PV1
Figure 250-2

Direct mode

Direct sample introduction permits a quantitative transfer of analyte without
risking contamination to the pneumatic system. It provides the sensitivity
required for air toxics analyses. The interface's minimal dead volume also
eliminates the potential interaction of solutes with poorly swept, active
surfaces.
In direct mode, the split vent is physically disconnected and the GC
reconfigured.
4 of 30
Split SPR
Vent Vent
SPR
FS
PS
PV2
Valve
closed
VI flow control diagram: splitless mode pneumatics (beginning of pre
run to sampling end- sample introduction in progress)
Inlets
Agilent 6890 Gas Chromatograph Service Manual
Sampler
Trap
To Column
Jun 2001