METHOD OF MEASUREMENT OF NITROGEN ISOTOPE RATIO IN NATURAL GAS

The method has been developed with which nitrogen is seperated by gas chromatograph and collected in a vacuum system, and isotope ratio of nitrogen are measured by mass spectrometry.The mean value of nitrogen isotope ratio of air in Lanzhou is 0.00368, with a standard deviation 0. 000053 (n= 7) , which is slightly higher than that of ¹⁵N/ ¹⁴N (0.00361) reported by Nier (1950) .The defference between the two measurements may be either due to analysing methods or may substantially reflects the natural phenomenon. While to the nitrogen Produced by 504 Factory in Lanzhou the mean value of ¹⁵N / ¹⁴Nis 0.00361, with a standard deviation 0.000050 (n = 5) . This method is an important means for geochemistry of natural gas, and through which the first batch of (δ¹⁵ N value of natural gas has been, so far obtained in China.