Paul,

We use 'exetainers' (Isochem, UK) routinely for breath sample
collection and there is no appreciable deterioration of the d13C
values over several days. However, for air samples that contain
clearly less CO2 that might be a different story.

The 'problem' with the caps is not to over-tighten them; fingertight
plus a 1/4 turn is ample. More than that and the septum will start
to bulge and buckle thus loosing the seal.

> We are testing Exetainers for collection and brief storage of air for CO2
> analysis.  There appears to be some small change in the values using the
> standard caps, although they may be usable with care.  Has anyone evaluated
> different caps for use with vials with Finnegan Mat's Gasbench II?

For gas analysis using a GC-IRMS setup with a CTC autosampler
and a Hamilton gastight syringe, I used GC autosampler vials
closed with butyl stoppers (Supelco), which I crimped shut.
Samples could be stored for about 7 days this way without d13C
deterioration but again I'm talking breath samples here.


Best wishes,

                          Wolfram



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Dr. W. Meier-Augenstein, CChem MRSC
Senior Research Fellow

University of Dundee, Dept. of Anatomy & Physiology,
Old Medical School, DUNDEE  DD1 4HN, United Kingdom

Tel. (B): +44-(0)1382-34/5124 or /4574
Fax  (B): +44-(0)1382-34/5514

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URL: http://www.dundee.ac.uk/anatphys/wma/meieraug.htm
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