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Journal of Automatic Chemistry
Volume 19, Issue 5, Pages 165-168
http://dx.doi.org/10.1155/S1463924697000175

Use of nitrous oxide as a purge gas for automated nitrogen isotope analysis by the Rittenberg technique

1Department of Natural Resources and Environmental Sciences, University of Illinois, Urbana, Illinois 61801, USA
2USDA-ARS, Urbana, Illinois 61801, USA
3Department of Crop Sciences, University of Illinois, Urbana, Illinois 61801, USA
4Department of Natural Resources and Environmental Sciences, Turner Hall, 1102 South Goodwin Avenue, Urbana, Illinois 61801, USA

Copyright © 1997 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

An apparatus that operates with an isotope-ratio mass spectrometer to automatically perform nitrogen isotope analyses by the Rittenberg technique was modified to permit the use of nitrous oxide (N2O) instead of Freon (CCl2F2 or CHClF2) for the purging of air prior to hypobromite oxidation of ammonium-N to N2 in a plastic microplate. Analytical performance was unaffected by the modifications. Up to 768 samples can be processed in a single loading, at a rate of 6 to 12 samples/h. Within the range of 0.2 to 20 atom % 15N, isotope-ratio analyses of 50 to 200 μg of N using the automated Rittenberg apparatus (ARA) with a double-collector mass spectrometer were accurate to within 0.7%, as compared to manual Rittenberg analyses of 1 mg of N using the same mass spectrometer with a dual-inlet system. Automated analyses of 20μg of N were accurate to within 2%, and automated analyses of 10 μg of N were accurate to within 7%. The relative standard deviation for measurements at the natural abundance level (10 analyses, 20-200 μg of N) was < 0.04 %.