Dear isotope geochemists,

we want to analyse the d18O of molecular oxygen in soil gases.
We use a mass spec equipped with a double inlet system.
The problem we are facing is to purify the oxygen for isotope analysis.

The only procedure for separation of oxygen from other gases (including nitrogen and noble gases) that I am aware of, involves conversion of oxygen to CO2.
If possible, however, I would like to analyse molecular oxygen.
(We run molecular oxygen extracted from silicates routinely on our mass spec, and it works fine)

Can anyone comment on one of the following questions or point out literature that could help ?!

(1) Are there any adsorbants, molecular sieves... that could selectively trap nitrogen and help to purify oxygen for isotope analyses?

(2) How clean must molecular oxygen be to get reliable results for d18O?

(3) What are the problematic interfearing species in the mass spec that could influence the d18O analysed?

Any comments are greatly appreciated!

Thanks.

Rainer


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Dr. Rainer Abart
Institut fuer Mineralogie-
Kristallographie und Petrologie
Karl-Franzens-Universitaet Graz
Universitaetsplatz 2
A-8010 Graz

Tel.: ++43-316-380 55 41
Fax:  ++43-316-380 98 65

e-mail: [log in to unmask]

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