User`s guide

Routine Maintenance
246
Sample Tubes and Storage Caps
When samples have been collected, the tubes should be analyzed as
soon as possible. If the tubes cannot be analyzed soon after
sampling, you should cap them with Swagelok caps (P/N 0496-
9332) and PTFE ferrules (P/N 0496-4467).
Avoid storing tubes that contain sample in places where there are
high levels of organic vapors, such as refrigerators and car trunks.
Tubes in such places must be capped with Swagelok caps.
Special precautions must be taken if the temperature of the sampled
tubes is expected to vary, or if altitude changes occur. In these cases
the contents of the tubes can be expected to expand and contract
under pressure changes. Poorly capped tubes may become
contaminated through temperature and pressure equalization, so it is
worth bearing this in mind when designing the experiment.
Sample tubes that have not been used for a while should be
reconditioned before use.
Keep storage caps in a clean environment (preferably a clean, heated
desiccator) when they are not on sample tubes. Although every
precaution is taken to ensure that new storage caps are clean, they
may adsorb organic vapors during storage or in transit.
You may want to heat new caps to 150°C for 2 to 3 hours before
putting them into use.
Requirements for Use with a Mass
Spectrometer
Sample tubes that have been used for atmospheric sampling contain
air and water, both of which are transferred to the cold trap of the
ATD/TD during the primary desorption process. To minimize the
air/water background on a mass spectrometer, run the sample tubes
with an outlet split of at least 10 mL/min. To reduce the background
further, heat the cold trap two or three times before the start of the
analytical sequence.
Additional improvement in the air/water background will be
obtained by substituting the graphite ferrules used on the cold trap