User`s guide

Routine Maintenance
281
glass filter disk (P/N L427-1290) can be used to separate
the layers. It may be possible to separate the two adsor-
bents with a plug of glass wool, but this will reduce the
volume of adsorbent that can be used.
7. It is normal not to use more than two adsorbents in the
cold trap, but if more are required, continue packing as
described above while making sure that added adsorbent
is stronger than the previous one.
8. Insert another 5-mm plug of glass wool in the open end
of the trap. Push the glass wool down using the packing
tool.
9. Replace the trap as outlined in Removing and Replacing
the Cold Trap on page 269.
10. Condition the trap before analytical use by heating it
several times with carrier gas flowing through it to
remove volatile impurities from the trap packing.
The trap is configured for backflush operation. In this configuration
the sample enters and exits the trap through the same end.
The volatile compounds travel through the weak adsorbent and are
held on the stronger adsorbent. During desorption, carrier gas flow is
reversed and the higher boiling compounds are desorbed from the
weak adsorbent, without contacting the stronger adsorbent.
Changing the Trap Filter Disks
Two porous, PTFE filter disks (P/N L1003030, pk/10) are installed
in the fittings at the end of the trap tube. These filter disks prevent
glass wool fibers, particles of adsorbent, or other trap waste material
from entering and damaging the heated valve and other parts of the
system.
CAUTION
Ensure that the glass wool plug is secure. If the plug is loose
the packing could move to a cooler part of the tube, resulting
in peak broadening or complete sample loss.
CAUTION
These filters are essential. Do not remove them under any
circumstances except to replace them with new filters.