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prepurge times are 1-
3 minutes for normal sorbents and materials samples and 10 minutes for molecular
sieves and carbonised molecular sieves.
3.6 Desorption modes
Two modes are available:
Standard 2(3) Stage Desorption
Tube Conditioning
Select between the modes by using the up and down arrows or
left clicking the desired option.
3.6.1 Tube conditioning mode
This mode is used to condition sorbent tubes prior to sampling.
Freshly packed sorbent tubes,
including the Tenax tube shipped with UNITY 2, will require conditioning
prior to use. There are several points to note when conditioning sample tubes using UNITY 2 as opposed
to an external Tube Conditioning/Dry-
dicated Tube Conditioning Mode so that contaminants from the tube are vented to the
charcoal filter and are not passed onto the cold trap.
Set the split flow to at least 50 ml/min (preferably 100 ml/min) to assist efficient conditioning.
heck the maximum isothermal temperature for the sorbent in use. We advise restricting
the conditioning temperature to at least 10°C below this sorbent maximum.
Set the flow path temp to at least 190°C while conditioning tubes. This prevents contaminants f
condensing inside the UNITY 2 flow path and helps to condition the system.
In tube conditioning mode, the cold trap is off line all the time so that desorbed materials cannot
contaminate this or the GC analytical column.
Method parameters may either
be entered by clicking on each box in turn, typing in the parameter and
then pressing Enter or by entering in the first parameter and then using the tab key to automatically enter
the parameter and move the cursor to the next active box. The last parameter
completed by pressing Enter.
Only a few of the usual thermal desorption parameters are relevant in a Tube Conditioning Method:
Set to Tube Conditioning.
Click on the box to enter a check if Split On in
Set Prepurge time by clicking in box and typing the required time. 1 minute
at 30 ml/min is enough to purge oxygen from most sorbent tubes. However,
this should be extended to 5 or 10 mins at 30 ml/min for molecular sieve
nd carbonised molecular sieve type sorbents.
Note: The cold trap is, by default, off line during ambient purge in tube
conditioning mode. The split flow is therefore switched on by default.
The desorb time
clicking in the relevant boxes and typing in the required values. The split
3 minutes for normal sorbents and materials samples and 10 minutes for molecular
sieves and carbonised molecular sieves.
Select between the modes by using the up and down arrows or
This mode is used to condition sorbent tubes prior to sampling.
including the Tenax tube shipped with UNITY 2, will require conditioning
prior to use. There are several points to note when conditioning sample tubes using UNITY 2 as opposed
Purge Rig (e.g. a TC20).
dicated Tube Conditioning Mode so that contaminants from the tube are vented to the
charcoal filter and are not passed onto the cold trap.
Set the split flow to at least 50 ml/min (preferably 100 ml/min) to assist efficient conditioning.
heck the maximum isothermal temperature for the sorbent in use. We advise restricting
the conditioning temperature to at least 10°C below this sorbent maximum.
Set the flow path temp to at least 190°C while conditioning tubes. This prevents contaminants f
condensing inside the UNITY 2 flow path and helps to condition the system.
In tube conditioning mode, the cold trap is off line all the time so that desorbed materials cannot
contaminate this or the GC analytical column.
be entered by clicking on each box in turn, typing in the parameter and
then pressing Enter or by entering in the first parameter and then using the tab key to automatically enter
the parameter and move the cursor to the next active box. The last parameter
change should always be
Only a few of the usual thermal desorption parameters are relevant in a Tube Conditioning Method:
Set to Tube Conditioning.
Click on the box to enter a check if Split On in Standby is required.
Set Prepurge time by clicking in box and typing the required time. 1 minute
at 30 ml/min is enough to purge oxygen from most sorbent tubes. However,
this should be extended to 5 or 10 mins at 30 ml/min for molecular sieve
nd carbonised molecular sieve type sorbents.
Note: The cold trap is, by default, off line during ambient purge in tube
conditioning mode. The split flow is therefore switched on by default.
- Time 1 - and desorption temperature -
clicking in the relevant boxes and typing in the required values. The split
3 minutes for normal sorbents and materials samples and 10 minutes for molecular
including the Tenax tube shipped with UNITY 2, will require conditioning
prior to use. There are several points to note when conditioning sample tubes using UNITY 2 as opposed
dicated Tube Conditioning Mode so that contaminants from the tube are vented to the
Set the split flow to at least 50 ml/min (preferably 100 ml/min) to assist efficient conditioning.
heck the maximum isothermal temperature for the sorbent in use. We advise restricting
Set the flow path temp to at least 190°C while conditioning tubes. This prevents contaminants f
In tube conditioning mode, the cold trap is off line all the time so that desorbed materials cannot
be entered by clicking on each box in turn, typing in the parameter and
then pressing Enter or by entering in the first parameter and then using the tab key to automatically enter
change should always be
Only a few of the usual thermal desorption parameters are relevant in a Tube Conditioning Method:
Set Prepurge time by clicking in box and typing the required time. 1 minute
at 30 ml/min is enough to purge oxygen from most sorbent tubes. However,
this should be extended to 5 or 10 mins at 30 ml/min for molecular sieve
Note: The cold trap is, by default, off line during ambient purge in tube
conditioning mode. The split flow is therefore switched on by default.
clicking in the relevant boxes and typing in the required values. The split
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