title: Gas chromatography/isotope-ratio mass spectrometry method for high-precision position-dependent 15N and 18O measurements of atmospheric nitrous oxide.
abstract: We describe an automated gas chromatography/isotope-ratio mass spectrometry (GC/IRMS) method for the determination of the (18)O and position-resolved (15)N content of nitrous oxide at natural isotope abundance. The position information is obtained from successive measurement of the isotopic composition of the N(2)O(+) ion at m/z 44, 45, 46 and the NO(+) fragment ion at m/z 30, 31. The fragment ion analysis is complicated by a non-linearity in the mass spectrometer that has to be taken into account. Evaluation of the absolute peak areas allows for a simultaneous determination of the N(2)O mixing ratio for atmospheric samples. Samples with mixing ratios ranging from a few nmol/mol up to the percent level can be analyzed using different sample inlet systems. The high concentration inlet system provides an easy and quick method to carry out various diagnostic tests, in particular to perform realistic linearity tests. A gas chromatographic set-up with a split column and a backflush possibility improves analytical precision and excludes interferences by substances with long retention times from preceding runs. We also describe a new open split interface that uses only a single transfer capillary to the mass spectrometer for sample and reference gas.
authors.affiliation: Max-Planck-Institut für Kernphysik, Bereich Atmosphärenphysik, Heidelberg, Germany. T.Roeckmann@mpi-hd.mpg.de
authors.forename: Thomas
authors.initials: T
authors.lastname: Röckmann
authors.forename: Jan
authors.initials: J
authors.lastname: Kaiser
authors.forename: Carl A M
authors.initials: CA
authors.lastname: Brenninkmeijer
authors.forename: Willi A
authors.initials: WA
authors.lastname: Brand
mesh_terms: D000388:Air / Q000032:analysis*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D009587:Nitrogen Isotopes; D009609:Nitrous Oxide / Q000032:analysis* / Q000737:chemistry; D010103:Oxygen Isotopes
chemical_list: D009587:Nitrogen Isotopes; D010103:Oxygen Isotopes; D009609:Nitrous Oxide