Dear Bill and other interested,

We use CO gas from Messer Griesheim (MG) with a purity of 4.7 (that
means 99.997 % CO) as reference gas for the carbon reduction technique
(pyrolysis or thermal conversion TC technique). The certified impurities
of this MG CO gas quality are O2 <= 3 vpm, N2 <= 5 vpm, H2O <= 3 vpm, H2
<= 1 vpm, hydrocarbons <= 2 vpm and Ar <= 7 vpm.
Your gas with 0.037 % O2 ( corresponds to 370 ppm O2) has a more than
100 times higher O2 content than the one that we use. I would suspect
some problems here: the O2 content is very critical because of its
reaction with N2 to NO in the ion source.
In my opinion an oxidative regime in the ion source of the mass spec
should completely be avoided during pyrolysis experiments; the ion
source should completely be held at a reductive regime. What are the
other impurities?
In my former institute we used CO 4.7 from Linde (impurities: N2 <= 5
vpm, O2 <= 5 vpm, Ar <= 15 vpm, H2 <= 1 vpm, hydrocarbons <= 2 vpm, H2O
<= 5 vpm). Both CO gases work successfully as reference gases for
CF-IRMS (EA- and GC applications). Our german CO gases have normally
d18O values around +8 per mill (at least the 4 bottles I used till now).

Best regards

Roland

P.S.: Maybe the following information is helpful:

There is a Messer Griesheim agency in Canada
http://www.respircare.com/
and one in the US
http://search.commerceinc.com/profile/id2091562496.html

Linde agencies can be found at:
http://www.linde.de/english/Homepage.htm

Maybe it is possible to order european or german CO gas at these
agencies

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Dr. Roland A. Werner
Max-Planck-Institut fuer Biogeochemie
Carl-Zeiss-Promenade 10, 07745 Jena, Germany
Postanschrift:
Postfach 10 01 64, 07701 Jena, Germany
Tel.: +49-3641-643719, -643825
Fax:  +49-3641-643710
e-mail: [log in to unmask]

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