About The Vi Direct Mode - Agilent Technologies 7890 Series Advanced Operation Manual

About the VI direct mode

Advanced Operation Manual
Purge flow The flow, in mL/min, from the split vent at Purge
time. You will not be able to access or specify this value if
your column is not defined.
Total flow When your column is defined, Total flow displays
the actual flow to the interface. You cannot enter a setpoint.
If your column is not defined, Total flow will have both
setpoint and actual values during purge time. All other
times, the actual flow to the interface is displayed.
Septum Purge Flow through the septum purge vent, at least
15 mL/min.
Gas saver On to reduce split vent flow at Saver time.
Saver flow Flow through the split vent after Saver time.
These instructions apply to both column defined and not
defined.
Press [Front Inlet] or [Back Inlet].
1
Scroll to Mode: and press [Mode/Type]. Select Splitless.
2
Set the interface temperature and a sampling end time.
3
If your column is defined, enter a Purge time and Purge
4
flow. Turn Gas saver on if desired. Set the Gas saver time
after the purge time and enter a Gas saver flow.
If your column is not defined, enter a Purge time (Purge
5
flow is not available). Set Total flow greater than column
flow plus septum purge flow to guarantee adequate
column flow.
Make certain Auto Prep Run is On (see
6
on page 40) or press [Prep Run] before introducing a
Run"
sample.
Direct sample introduction permits a quantitative transfer of
analyte without risking contamination to the pneumatic
system. It provides the sensitivity required for air toxic
analyses. The interface's minimal dead volume also
eliminates the potential interaction of solutes with poorly
swept, active surfaces.
To operate in the direct mode, you must physically
disconnect the split vent and reconfigure the GC.
3
Inlets
"Pre Run and Prep
137