Abstract: Mass spectrometry was developed to determine the enrichment of stable isotope ¹⁵N labeled compounds in which the treatment of samples are crucial. Nitrogen as sample forms has the advantages of smaller memory effect and no isotope fractionation. Typical ¹⁵N inorganic and organic compounds were chosen for the research of sample treatment by the methods of hypobromite redox reaction, semi-micro digestion-redox reaction and microscale high temperature combustion method. Isotope fractionation and memory effects occurred in conversion of samples were eliminated and the accuracy and precision of the results were satisfying. In the research feasible sample conversion conditions and operation procedure were obtained. Mass spectrometry data were tested by mathematical statistics with satisfactory result.