Hi Todd,

In our lab we use both a COSTECH 4010 and a Isotope CUBE for wt% and 
isotopes of CN.   The manufacturers recommended oxidation catalysts are: 
chromium oxide and copper oxide in the COSTECH and CUBE respectively.  I 
run the COSTECH combustion at 1000oC and the CUBE at 950oC.  I see no 
difference in the quality of the data, and assume there is little 
difference between the efficacy of these oxidation catalysts ...

FWIW: I have tried measuring 15N of sediment (ground whole rock) 
containing <0.05 wt%N using a single reactor on the COSTECH 4010 (also 
chromium oxide + reduced copper + silvered cobaltous/ic oxide as 
described in the Costech manual), but the 15N data was 
inconsistent/poor.  My suspicion/assumption(?) is that there isn't 
enough copper at the correct temp (600 to 650oC) in the single reactor 
configuration, but it could also have just been the samples (!?!).  FYI: 
I was only interested in 15N and have no data on the quality of the 13C 
using a single reactor.

Any particular reason you're attempting CN of plant material on a single 


On 04/01/2016 9:35 AM, BROWN, TODD M [AG/1005] wrote:
> Has anyone compared chromium vs. copper oxide as the oxidation 
> catalyst in a Flash 1200? I used copper oxide without any difference 
> in % and isotope CN results when I was running a 2 tube setup that had 
> the reduced copper in the second tube, however, I have switched to a 1 
> tube packing scheme so there is not enough room for a lot of any 1 
> catalyst. The 1 tube packing goes chromium oxide, reduced copper, 
> silvered cobaltous/ic oxide as describe in the Flash manual. Since I 
> accidentally ordered a large amount of copper oxide (I really need to 
> pay better attention sometimes) I was thinking of using it for the 
> chromium in this configuration. My samples are typically 2 mg of dried 
> plant material.
> Todd Brown
> Monsanto
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> Chesterfield MO 63017
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> FAX 636 737-4844
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Stephen Taylor
University of Calgary
Department of Geosciences
Applied Geochemistry - Isotope Science Lab
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