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QUI-1057
Page 52
Markes International Ltd
T:
+44 (0)1443 230935
F:
+44 (0)1443 231531
E:
www.markes.com
5.2.4
Long term storage of clean and sampled tubes
Conditioned or sampled tubes should always
be stored using ¼-inch brass Swagelok-type
screw caps fitted with combined PTFE ferrules
(C-CFO20 (pk20), C-CF200 (pk200)). It is
recommended that these be tightened by
hand plus a further quarter turn using
conventional spanners or ideally a Markes
International Ltd. CapLok tool (C-CPLOK).
It is not necessary to store capped tubes in refrigerated conditions unless they are sampled, multibed
tubes in which case refrigeration may be required to prevent analyte migration to the stronger sorbents.
In fact in most cases differential contraction of the tubes and seals at fridge or freezer temperatures can
cause the caps to come loose. If refrigeration is to be used, caps must be retightened (a quarter turn)
once they have reached their storage temperature.
NOTE
: A tube should be allowed to warm up and equilibrate properly at ambient temperature before the
beginning of sampling. If this is not done, a significant mass of water from the atmosphere will be retained
in the tube via simple condensation.
NOTE
: If tubes are to be transported in such a way as to be exposed to very cold temperatures, it is
advisable to follow the above retightening procedure by cooling the tubes prior to shipment. When
monitoring trace level atmospheric components, conditioned and sampled tubes can be wrapped in
uncoated aluminum foil and / or placed in a sealed, non-outgassing container, such as an uncoated tin,
during transportation and storage.
5.2.5
Changing tube seals and filters
The tube O-ring seals (U-COV10 (pk 10), U-
COV100 (pk 100)) are found at either end of
the tube sealing mechanism. UNITY should be
switched off before O-rings are removed or
replaced.