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Stable Isotope Geochemistry

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Subject:
From:
"Carl G. Johnson" <[log in to unmask]>
Reply To:
Stable Isotope Geochemistry <[log in to unmask]>
Date:
Wed, 25 Feb 2004 11:21:16 -0500
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Has anyone experienced outgassing of CO2 during the heating or sealing
of quartz or pyrex tubing?

We have recently been trying to seal such tubes and have noted a
heating-temperature dependent CO2 background in our blanks. We can
monitor this by other means (flushing the contents of the tube into a
Licor CO2 meter) and see that if we even just flame the tubes above
about 500c, we observe a CO2 signal. Repeated heating of the same area
results in progressively lowered signals, so this is not a leak, but
rather something coming out of the glass itself. Fully melting the tube
to seal it generates an unacceptably large blank for our purposes. The
effect can be somewhat reduced by working with tubes that are
pre-constricted with a *very* thin wall in the area to be melted.

Thanks for any input you may all be able to offer.

Carl Johnson
Research Specialist
Woods Hole Oceanographic Institution
Woods Hole, MA
USA
02543-1543

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