摘要
Samples of a certain stable compound of accurately known concentrations of nitrogen-15 may be used for the quality control of 15N products in the isotopic separation plant. The present investigation aims to prepare a sample of ammonium sulfate with nitrogen-15 concentration of about 98 atom％ 15N. Together with the known content of （NH4）2SO4 of the sample and of the natural ammonium sulfate, any sample of 0.366 to 98 atom％ 15N can be obtained by blending for the calibration of the mass spectrometer.
