INFICON Explorer Portable Gas Chromatograph - Manual (Page 248)

Maintenance and Troubleshooting
246
Flushing the Columns
NOTE: To avoid system contamination, do not allow the internal carrier gas cylinder to
empty completely.
By definition, column packing or coating materials are very efficient adsorbers of
chemicals. If a column is left without continuous gas flow, contaminants present in
the air may enter through the ends of the column. These contaminants will
accumulate and when the column is put back into service the resumed flow of carrier
gas will carry a high concentration of contaminants into the detector. This will
decrease as the column cleans, but levels may be sufficiently high, initially, to
saturate the detector.
Saturation has occurred when the offset level is greater than 800 mV. At this point
the signal level can no longer be set to 10% of full scale at the start of an analysis.
Saturation can also occur if many high concentration samples are analyzed in
succession.
Saturation can often be reduced or eliminated by allowing carrier gas to flush the
column and detector for a few hours. Normally, columns that are not in use are
flushed with a low flow of carrier gas. If possible, you can take the contaminated
column out of service and use the remaining columns to run analyses. The
contaminated column will eventually be flushed and be available for use. To speed
up the flushing process, you may increase the carrier gas flow through the
contaminated column. If you use this procedure, you will not be able to run analyses
on the instrument while the columns are flushing.
Flushing a Single Column
1. Move the instrument to an area where the ambient air contains no VOCs.
2. If the instrument is auto-analyzing, disable that option.
3. Switch to supervisor mode by pressing Enter Menu, then SETUP and MODE,
then use the arrow keys to select Super.
4. Press Enter Menu and Exit.