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| Performance Tip Featured in Issue 20.2 |
| Conditioning Thermal Desorption Tubes |
Thermal desorption tubes have an advantage over solvent desorption tubes
since they are reusable. However, after using a thermal desorption tube,
it is necessary to properly recondition the tube. You must heat the tube
and completely remove the sample from the previous application before using
the adsorbent tube again.
We recommend that you condition the tube at 10 to 20°C above the desorption
temperature you use to analyze the tube. When conditioning, make sure that
you do not exceed the recommended maximum temperature limit of the absorbent.
Use clean nitrogen or helium at a flow rate of 50cc/minute for at least
thirty minutes. More time may be necessary depending on how you use the
tubes.
If you are sampling in the parts per billion or parts per trillion range
you may need to condition your tubes for two or three hours. Longer conditioning
times are also required after too much sample is adsorbed onto the tube.
When you are conditioning a multi-bed tube, you want to make certain that
the direction of the gas flow during conditioning is correct. The direction
of the flow should go from the strongest bed of adsorbent through the weakest.
This removes high molecular weight analytes that collect on the inlet of
the tube. Otherwise, these analytes are irreversibly adsorbed on the other
beds. - Jamie Brown - Research
& Development |
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For more information,
see |
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T402025
(1,817 KB) "A Tool for Selecting an Adsorbent for Thermal Desorption
Applications" |
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