Stable Isotope Geochemistry


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Jonathan Karr <[log in to unmask]>
Reply To:
Stable Isotope Geochemistry <[log in to unmask]>
Tue, 17 Feb 2004 11:24:10 -0500
text/plain (78 lines)
I will second what Gilles said about the dual inlet for CO. We've been
using this method for running the TC/EA for nearly two years with excellent
results. The only thing to be cautious of is that you start each run with a
fresh aliquot of reference CO set up so that with the bellow fully
expanded, you have close to the maximum usable voltage signal. That way,
any gas depletion and isotopic drift during the run will be minimized. You
can refill the bellow to the appropriate pressure (about 80 mBar for us)
probably hundreds of times  with a lecture bottle, using the dual inlet
valves to introduce and equilibrate a small volume from the bottle. We will
refill the lecture bottle when needed from a large tank of Messer CO stored
inside a fume hood.

At 08:50 AM 2/17/2004 +0100, you wrote:
>Dear list members,
>We are in the process of setting up a CF-IRMS system (Delta + XP, gas bench,
>TC-EA and flash EA) in our laboratory. We are somewhat uncertain as to the
>best design for the CO gas suppyling system, in terms of efficiency and
>If you have gone through this as well, we would like to hear about your
>choices in terms of storage of CO tank (inside, outside, security
>locker....), as well as tubing, vannes and purging system for the gas
>delivery line. We presently have a quotation from a major gas supplier which
>is outrageously expensive and we are looking for less costy, but fully
>secure, alternatives.
>Please, reply directly to me at [log in to unmask]
>Jean-Pierre Girard
>Isotope Geochemistry Unit
>3 avenue C. Guillemin - BP 6009
>45060 Orléans cedex 2 - France
>Tél. : - Fax :
>e-mail : [log in to unmask] - web : <>
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Jonathan D. Karr, Ph.D.
Technical Director, Duke EnVironmental stable Isotope Laboratory (DEVIL)
Duke University Dept.of Biology & Nicholas School of the Environment and
Earth Sciences
National Phytotron, Box 90340
Durham, NC 27708-0340
(919) 660-7418
Fax: (919) 660-7425
[log in to unmask]
laboratory website:

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