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.
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"
Tel.: +49 431 609 2224
Fax: +49 431 609 2300
E-mail: [log in to unmask]
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.
700 Chesterfield Pkwy
Chesterfield MO 63017
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