Daily Operation
To shut down the GC
Released: March 2004 6850 Series II GC User Information page 53 of 256
Multi Valve with sample valve and a sequence
1. The sample valve is in the Load state between runs. The Not Ready light is
on during this period. Connect the sample streams to the Multi Valve.
2. Set up the valve sequence. See the Control Module or ChemStation/Cerity
Chemical documentation for details.
3. The "Ready for sequence" message appears when the GC is ready, but it is
not necessary to wait for it. Press Start. The Multi Valve steps through
the range of positions specified by the sequence, and the sample valve
injects each one into the GC.
To shut down the GC
For a short period (including weekends)
1. Wait for the present run to finish.
2. If the active method has been modified since it was loaded, there will be a
+ symbol following its name. To save these changes, use a Control Module
or ChemStation/Cerity Chemical.
3. Leave the main power switch on. This keeps the heated zones at their
setpoint temperatures so that the GC will be ready for use when needed.
4. Turn off all gases, except the carrier, at their sources. Leave the carrier on
to protect the column from atmospheric contamination.
5. If cryogenic cooling is used, you may want to turn the cyro coolant off.
6. This is an excellent time to replace the septum (see “Changing septa” on
page 121).
For a long period
1. Perform all the steps above.
2. Turn the carrier gas off at the source.
3. Turn the main power switch off.
4. Allow time for the oven to cool.
5. Remove the column from the oven. Cap both ends to keep contaminants
out.
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