User guide

Columns and Oven 9
Advanced User Guide 291
If using an Agilent data system, a Backflush Wizard provides a
straightforward interface for making these settings.
1 Verify that all columns are properly configured.
2 Since the backflush will run as a post- run program, set the
method so that the oven program ends after the last peak of
interest returns to baseline, or after reaching the last
temperature of interest.
3 Press [Post Run] and enter the backflush duration as the Time.
• The oven temperature and column pressure/flow
setpoints for installed columns appear.
• Whether you can enter a pressure or flow for a column
depends on its mode (pressure or flow).
4 Enter the oven temperature for the backflush.
5 Enter the backflush flow(s) or pressure(s).
If in flow mode:
• Enter a negative flow for the column connected between
the inlet and the CFT device. The GC will automatically
establish the corresponding pressures needed in the inlet
and the CFT device.
• Increase the flow rates in the column(s) connected
between the CFT device and the detector(s).
If in pressure mode:
• Set the pressure of the column connected between the
inlet and the CFT device to 0.000. This turns off flow from
the inlet.
• Increase the pressure of the primary column connected
between the CFT device and the detector(s). This creates
the backward flow through the column and increases the
flow through any connected detectors.
When developing the backflush portion of your method,
consider the following:
• Ensure that the split vent flow setpoint is at least 25 mL/min
and at least 50% more than the column backflush flow rate.
• If using gas saver, ensure that the gas saver flow setpoint is at
least 25 mL/min and at least 50% more than the column
backflush flow rate.