The determination of the nitrogen content and nitrogen-15 abundance by means of the nitrogen gas generated from inorganic and organic materials

A method is described for the determination of the total nitrogen content, after conversion to nitrogen gas, of various types of samples before the mass-spectrometric analysis of the ¹⁵N abundance. The sample is burned with a mixture of copper oxide, copper and lime in a closed tube under vacuum (modified Dumas method). The gas is released into an evacuated chamber of known volume and the nitrogen pressure is used to determine the nitrogen content of the sample. The gas is then admitted into a mass spectrometer. In order to obtain complete combustion of the material and to generate pure nitrogen gas, various combustion temperatures, combustion times and oxidizing agents were compared.