title: Interlaboratory assessment of nitrous oxide isotopomer analysis by isotope ratio mass spectrometry and laser spectroscopy: current status and perspectives.
abstract: BACKGROUND
  In recent years, research and applications of the N2O site-specific nitrogen isotope composition have advanced, reflecting awareness of the contribution of N2O to the anthropogenic greenhouse effect, and leading to significant progress in instrument development. Further dissemination of N2O isotopomer analysis, however, is hampered by a lack of internationally agreed gaseous N2O reference materials and an uncertain compatibility of different laboratories and analytical techniques.
  
  
  METHODS
  In a first comparison approach, eleven laboratories were each provided with N2O at tropospheric mole fractions (target gas T) and two reference gases (REF1 and REF2). The laboratories analysed all gases, applying their specific analytical routines. Compatibility of laboratories was assessed based on N2O isotopocule data for T, REF1 and REF2. Results for T were then standardised using REF1 and REF2 to evaluate the potential of N2O reference materials for improving compatibility between laboratories.
  
  
  RESULTS
  Compatibility between laboratories depended on the analytical technique: isotope ratio mass spectrometry (IRMS) results showed better compatibility for δ(15)N values, while the performance of laser spectroscopy was superior with respect to N2O site preference. This comparison, however, is restricted by the small number of participating laboratories applying laser spectroscopy. Offset and two-point calibration correction of the N2O isotopomer data significantly improved the consistency of position-dependent nitrogen isotope data while the effect on δ(15)N values was only minor.
  
  
  CONCLUSIONS
  The study reveals that for future research on N2O isotopocules, standardisation against N2O reference material is essential to improve interlaboratory compatibility. For atmospheric monitoring activities, we suggest N2O in whole air as a unifying scale anchor.
authors.affiliation: Laboratory for Air Pollution & Environmental Technology, Empa, Überlandstr. 129, CH-8600, Dübendorf, Switzerland.
authors.forename: Joachim
authors.initials: J
authors.lastname: Mohn
authors.forename: Benjamin
authors.initials: B
authors.lastname: Wolf
authors.forename: Sakae
authors.initials: S
authors.lastname: Toyoda
authors.forename: Cheng-Ting
authors.initials: CT
authors.lastname: Lin
authors.forename: Mao-Chang
authors.initials: MC
authors.lastname: Liang
authors.forename: Nicolas
authors.initials: N
authors.lastname: Brüggemann
authors.forename: Holger
authors.initials: H
authors.lastname: Wissel
authors.forename: Amy E
authors.initials: AE
authors.lastname: Steiker
authors.forename: Jens
authors.initials: J
authors.lastname: Dyckmans
authors.forename: Lars
authors.initials: L
authors.lastname: Szwec
authors.forename: Nathaniel E
authors.initials: NE
authors.lastname: Ostrom
authors.forename: Karen L
authors.initials: KL
authors.lastname: Casciotti
authors.forename: Matthew
authors.initials: M
authors.lastname: Forbes
authors.forename: Anette
authors.initials: A
authors.lastname: Giesemann
authors.forename: Reinhard
authors.initials: R
authors.lastname: Well
authors.forename: Richard R
authors.initials: RR
authors.lastname: Doucett
authors.forename: Chris T
authors.initials: CT
authors.lastname: Yarnes
authors.forename: Anna R
authors.initials: AR
authors.lastname: Ridley
authors.forename: Jan
authors.initials: J
authors.lastname: Kaiser
authors.forename: Naohiro
authors.initials: N
authors.lastname: Yoshida
mesh_terms: D000465:Algorithms; D005740:Gases / Q000032:analysis / Q000737:chemistry*; D007834:Lasers; D013058:Mass Spectrometry / Q000379:methods / Q000592:standards / Q000639:trends; D009587:Nitrogen Isotopes / Q000032:analysis / Q000737:chemistry*; D009609:Nitrous Oxide / Q000032:analysis / Q000737:chemistry*
chemical_list: D005740:Gases; D009587:Nitrogen Isotopes; D009609:Nitrous Oxide