User`s guide

Theory of Thermal Desorption
315
Two Stage Desorption (PerkinElmer ATD)
Figure 94 Cryofocusing on Capillary Tubing
Figure 95 Trapping on a Packed Cold Trap (TD and ATD)
Both of these procedures reduce the component bandwidths and
improve the efficiency of the chromatographic separation. However,
of the two methods, trapping on a packed cold trap has the following
significant advantages:
It can be used for both packed and capillary chromatography.
When the system is connected to narrow bore capillary columns, the
peak widths obtained are comparable to those produced by
conventional capillary column injectors.
During tube desorption of samples containing water or on-line air
sampling, ice tends to collect at the secondary refocusing part of the
system. Deposition of ice in the wider bore tubing of a packed cold
trap is much less likely to restrict or block the carrier gas flow path
than it is in the capillary tubing of a cryofocusing system. This is
important for many thermal desorption applications, especially those
GC
Analytical
Column
Hot Sample
Tube
Inlet
S
plit
(optional)
O
utlet
S
plit
(optional)
Carrier
Gas
Inlet
GC Detector
Capillary
Cryofocusing
Device
GC
Analytical
Column
Hot Sample
Tube
Inlet Split
(optional)
Outlet Split
(optional)
Carrier
Gas
Inlet
GC Detecto
r
Cold Trap