Volume 14 (1998) Issue 3 Pages 485-491
A system for the isotopic measurement of nitrogen at the sub-nanomole level has been developed using a modified noble gas mass spectrometer, allowing 40Ar/36Ar, N2/40Ar, 4He/40Ar and C/N ratios as well as the δ15N value to be measured on one sample. Moreover, carbon dioxide can be collected for a δ13C measurement. The experimental details concerning the analytical system are presented here, including the nitrogen purification procedure and its performance. The analytical errors concerning the δ15N values and 28N2/40Ar ratios were estimated to be about 0.3‰ and 3‰ for actual samples. Using six basalt glasses, the ability of the instrument to make accurate nitrogen isotope measurements has been evaluated. The observed values of the nitrogen content, nitrogen isotopes and nitrogen/argon ratios are compatible with the data in the literature. The results of some basic experiments and the observation of basalt glasses demonstrate that the new system can be applied to measuring nitrogen isotopes in geochemical and environmental samples.