User`s guide

Theory of Thermal Desorption
311
Figure 91 Tube Purge
When purging a tube prior to desorption under the tube or trap
conditioning modes, the purge gas does not flow through the cold
trap.
After the purge time has elapsed, the oven is brought into contact
with the sample tube and the desorb time is started. If an Internal
Standard Addition accessory is being used, the injection of the
standard takes place before the tube is desorbed.
Heated Purge—During heated purge the sample tube is heated to
remove moisture and low boiling solvents. The tube is purged with
carrier gas as would normally be the case, but the oven is brought
into contact with the tube during the purge time and the tube is
heated to the purge temperature for the duration of the purge time.
Reverse Dry Purge—If the Internal Standard Addition accessory
is installed, a reverse dry-purge can be performed. This is different in
that the tube is purged in the sampling direction i.e. from weak
Desorb
Flow Vent
T
r
a
n
s
f
e
r
L
i
n
e
T
o
G
C
SV2
Carrier
Supply
SV1
Desorb Supply
Carrier
Pressure
Trap
Pressure
Regulator
2
3
4
1
Leak
Pressure
Supply
SV4
Outlet Split
SV5
Inlet Split
SV3
Desorb Vent
Inlet Split/
Tube Condition Vent
Outlet Split
Vent
Valve A
Position A
A
Sample
Tube