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Dear Victor,

I think it`s Cr2O3 and not CrO3.
And Cr2O3 is not the (main) oxidant (own experience: definitely not at 
all a quantitative CO production at 1450 °C with carbon reduction 
technique). According to Pella and Colombo (1973; Mikrochimica Acta 
[Wien] 1973, 697-719) the silver in the cobaltous oxide fraction gives a 
"better mechanical resistance" at temperatures >750 °C. The silver is 
additionally effective in "retaining halogens (except fluorine) and 
sulphur oxides". The Cr2O3 can easily be used "up to temperatures of 
1800-1900 °C".
Many years ago we used a Roboprep system, similar to the Sercon system 
you described, with  a similar filling with a.o. CuO. Sometimes (often 
?) we had problems with leakage at the point where CuO and quartz come 
in contact (possible reason --> building of an eutectic system  between 
<SiO2> and <CuO> ??) depending also on quartz quality and applied 
temperature (problems were solved by introducing a Ni sheet). CuO easily 
releases O2 at higher temperatures; I think already at temperatures > 
800°C, which would reduce the life-time of the filling of the oxidation 
reactor and could lead to not constant oxidation conditions and a 
reduced life-time of the reduction tube.
There is an interesting review article (in German) about the "history" 
(with e.g. pros and cons of catalysts etc.) of elemental analysis by I. 
Monar in Microchimica Acta, Heft 2 (1965), 208-249.
Best regards

Roland

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Papers in 2015:

The relationship between needle sugar carbon isotope ratios and tree
rings of larch in Siberia
(free access at the moment)
http://treephys.oxfordjournals.org/cgi/reprint/tpv096?ijkey=LNjo87Wp2OvIpbZ&keytype=ref 


Malate as key carbon source of leaf dark-respired CO2 across different
environmental conditions in potato plants (free access)
http://jxb.oxfordjournals.org/content/66/19/5769.full.pdf+html

Allocation dynamics of recently fixed carbon in beech saplings in
response to
increased temperatures and drought (free access)
http://treephys.oxfordjournals.org/content/35/6/585.full.pdf+html?sid=4454cd3b-b5c1-4575-9075-44da4e4abfea 


Multifactorial in vivo stable isotope fractionation: causes, correlations,
consequences and applications (limited free access)
http://www.tandfonline.com/eprint/DEZ3TmbQqvUqVFqqm7as/full
in case if the pdf is not available anymore pls check on researchgate:
http://www.researchgate.net/profile/Roland_Werner/

Changes in d13C of dark respired CO2 and organic matter of different
organs during early ontogeny in peanut plants (limited free access)
http://www.tandfonline.com/eprint/6WUmBtH42ZHUAVr46IXN/full
in case if the pdf is not available anymore pls contact me per email

Multi element (C, H, O) stable isotope analysis for the authentication
of balsamic vinegars (limited free access)
http://www.tandfonline.com/eprint/DEZ3TmbQqvUqVFqqm7as/full
in case if the pdf is not available anymore pls contact me per email

Editorial "Special Issue dedicated to Prof. Hanns-Ludwig Schmidt on the 
occasion
of his 85th birthday" (open access)
http://www.tandfonline.com/eprint/I2hIdGxU8yZIcJ2VIiRV/full
in case if the pdf is not available anymore pls contact me per email

Does fog chemistry in Switzerland change with altitude?
(in case you are interested pls send an email)
http://www.sciencedirect.com/science/article/pii/S0169809514000866


Special issue dedicated to Prof. Hanns-Ludwig Schmidt
http://www.tandfonline.com/toc/gieh20/51/1


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Dr. Roland A. Werner
Institut fuer Agrarwissenschaften
Massenspektrometer-Labor
ETH Zuerich, LFW C48.1
Universitaetsstrasse 2
CH-8092 Zuerich
Schweiz

Tel. Buero:  ++41/(0)44/632 6754
Tel. IsoLab: ++41/(0)44/632 6694

e-mail:[log in to unmask]

URL:    Personal ETH website
         http://www.gl.ethz.ch/people/person-detail.html?persid=116463
         Researchgate Account
         http://www.researchgate.net/profile/Roland_Werner/
         Academia.edu Account
         https://independent.academia.edu/RolandWerner

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On 05.01.2016 12:25, Victor Evrard wrote:
> Dear All,
>
> After working with Sercon systems and now Thermo systems for EA-IRMS, 
> I have been meaning to ask this question regarding the suggested use 
> of CrO3+Silvered cobaltous oxide and CrO3+CuO+Ag wool for the 
> oxidation reactor by Thermo and Sercon, respectively.
> What is the difference?
>
> Thank you and happy new year!
> Victor
> --
> Victor Evrard, PhD
> Lab Manager | BASIEL
>
> Sustainable Land Use Group | Department of Environmental Sciences
> University of Basel
> Schönbeinstrasse 6
> CH-4056 Basel
> Switzerland
>
> http://goo.gl/cl6x97
> +41 61 267 35 17