Natural 15N abundance measurements and atmospheric nitrogen standard calibration

摘要: Small differences in natural isotope ratios between two compounds can be measured easily and with high precision by using mass spectrometers fitted double (or triple) ion collectors dual inlet systems equipped for rapid switching reference sample1–3. The parameter used to describe these 15N abundance is: where R is the isotopic ratio of m/z = 29(14N15N+) 28(14N14N+). Although an international standard nitrogen has not yet been defined, atmospheric N2 had chosen through practical experience, even before worldwide homogeneity its composition was demonstrated4–7. However, presence argon (≃1%) purified air samples may, some circumstances, modify apparent N2. Two different our laboratory have assess magnitude this ‘argon effect’, which seems essentially instrumental, presumably pressure-related, effect. Therefore, on showing effect it imperative that a correction applied measurements δ15N circumstances (different spectrometers, tuning same instrument) non-existent or negligible might require no whatsoever.