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 reactor?

Cheers,
Steve

On 04/01/2016 9:35 AM, BROWN, TODD M [AG/1005] wrote:
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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

Office 636 737-6397

FAX 636 737-4844

 



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