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Hi Todd,

We have a Flash 1112 with a two tube setup. When using copper oxide instead of chromium oxide in the oxidation tube, we obtained  inconsistent d15N results with the standards IAEA-N1 and IAEA-N2 in the past. The difference between the standards we found in 2002 using copper oxide was 1 lower than expected, what was confirmed by analyses made at Thermo in Bremen back then. The deviation from the expected difference using chromium oxide typically is 0.01-0.02 in my lab. However, a drawback of using chromium oxide is that the quartz tubes regularly crack when cooled down.

Cheers,
Joachim


.......................................................................................
Dr. Joachim Molkentin
Max Rubner-Institute (MRI)
Federal Research Institute of Nutrition and Food
Department of Safety and Quality of Milk and Fish Products
Section "Isotope and Lipid Analysis  -  Product Identity"
Hermann-Weigmann-Str. 1
24103 Kiel
GERMANY

Tel.: +49 431  609 2224
Fax: +49 431  609 2300
E-mail: [log in to unmask]
www.mri.bund.de



Von: Stable Isotope Geochemistry [mailto:[log in to unmask]] Im Auftrag von BROWN, TODD M [AG/1005]
Gesendet: Montag, 4. Januar 2016 17:35
An: [log in to unmask]
Betreff: [ISOGEOCHEM] Chromium vs. Copper Oxide

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
700 Chesterfield Pkwy
Chesterfield MO 63017
Office 636 737-6397
FAX 636 737-4844





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