User guide

Columns and Oven 9
Advanced User Guide 289
Backflushing a Column
Backflush is a means of discarding high- boilers from a column
after the peaks of interest have eluted. It saves analysis time
and has these additional benefits:
• Longer column life
• less high temperature exposure
• removal of high- boilers
• protection from air and water at high temperatures
• Less chemical background
• ghost peaks
• “wrap- around” of late eluters from previous runs
• stationary phase decomposition peaks
• Less contamination of the mass selective detector (MSD)
source, if using MSD
• longer time between source cleanings
• higher stability of calibrations
You will need to experimentally determine the correct
flow/pressure settings and the backflush time appropriate for
your analysis. Determine the correct values by testing the
backflush method, then running a blank to check for residual
late eluters.
Refer to the Agilent web site at http://www.agilent.com/chem
for example backflush applications, especially if using an MSD.
Backflushing when connected to an MSD
If using an MSD with the GC, backflushing becomes more
complex. Set up backflush as a post run event by using the
Backflush Wizard present in the MSD Productivity
ChemStation.
CAUTION
Only backflush an inlet that has a split vent line with a chemical trap,
such as the split/splitless, PTV, and VI. Attempts to backflush using
other inlet types will most likely damage the pneumatics flow
modules.