While our system is optimized for the bacterial denitrifier method and the reference materials therein, we are open to running vials containing N2O that outside researchers have prepared themselves. These may be nitrate samples that were converted to N2O via the same bacterial denitrifier method or by the azide reduction method. Users submitting samples for this analysis are responsible for providing their own standards for calibration. Samples can either be analyzed as N2O for δ15N and δ18O or as O2 and N2 for δ15N, δ17O, and δ18O.
Samples should be submitted in 20-mL, septum-sealed vials with a minimum of 40 nmoles N2O if they are to be analyzed as N2O or a minimum of 400 nmoles N2O if they are to be analyzed as O2 and N2. See the table below for sample analysis pricing.
Exhaustive description of analysis
Vials are loaded onto a GC PAL autosampler. Each vial is purged with helium, forcing the effluent through a cold water trap (-60 °C), a carbon dioxide, water chemical trap (Ascarite, Magneiusm perchlorate), a volatile organic compound trap, and a liquid nitrogen trap, before a vent. All sample / standard N2O remains in the liquid nitrogen trap and is moved into a secondary focusing liquid nitrogen trap. A dochotomy exists from here.
Intact N2O for δ15N and δ18O - If samples are to be analyzed for δ15N and δ18O only, the cryofocused N2O moves through a porapaq Q gas chromatography column for separation with any remaining CO2 and then into a Thermo Finnigan Delta Plus for mass / charge 44, 45, and 46 measurement.
Pyrolyzed N2O for δ15N, δ17O and δ18O - If samples are to be analyzed for δ15N, δ17O and δ18O, the cryofocused N2O moves through a gold tube held at 800 °C which pyrolyzes the N2O into O2 and N2. These two species are then separated in a 5A molecular sieve gas chromatography column and then sent into the isotope ratio mass spectrometer for mass / charge 32, 33, 34 and then 28, 29 measurement