The determination of nitrogen-15 by emission and mass spectrometry in biochemical analysis: a review

Optical spectroscopy with photo-electric detection provides a rapid and precise micromethod for determining the nitrogen isotopic concentration of nitrogen gas and of nitric oxide gas. This paper describes the effect of operating conditions on the precision and the accuracy of such measurements. A determination can be made on a sample of 20 cc at a pressure of 1.5 mm of mercury (0.04 cc-atm) in approximately 10 minutes, to an accuracy of a few per cent. (auth)

Stable Nitrogen Isotope Analysis by Optical Spectroscopy

Plasma emission sources in analytical spectroscopy—II

Analyse isotopique de l'azote par spectrometrie optique, pour de faibles teneurs en 15n

Two emission spectrometers, a modified Hilger Watts-quartz spectrograph and a commercially available N15-analyser (type NO1-4) were tested with standard gas samples, whose N15-contents in the range of natural (0.365%) to about 80% N15 abundance were also determined by mass-spectrometry. Both optical instruments make use of the isotope effect in the electronic-vibrational spectrum of nitrogen in the far ultra-violet. Sample preparation has to be carefully considered. The total amount of nitrogen required to determine easily a N14/15 ratio by the emission spectrographic method is only about 10 µg. This corresponds to a total weight of plant material of under 1 mg and at this level homogeneity questions are very important. It is necessary to use a sample of at least 100 mg to reduce uncertainty due to inhomogeneity to well under the levels of field agricultural variation (±5%). With this quantity of sample, both the Kjeldahl method (followed by the Rittenberg conversion of ammonium to nitrogen) and the dry Dumas method are equally satisfactory.

Emission spectrometry for routine analysis of nitrogen-15 in agriculture

Es wird eine Methode beschrieben, um Konzentrationen der Stickstoffisotope 15N und 14N mit nur 50 γ N2 durch Photometrierung ultravioletter Banden zu bestimmen. Der mittlere Fehler betragt etwa ± 2% bei Berucksichtigung der Schwarzungsverhaltnisse. Die gewohnlichen Verunreinigungen beeinflussen die Resultate nieht.

Hermann‐Rolf Weisser

Papers

Reaktionen mit 15N. II. Eine spektroskopische Mikromethode zur Bestimmung von 15N