Hello Brian,
you might check the following reference. 
Westley, M. B., Popp, B. N., Rust, T.M., 2007. The 
calibration of intramolecular nitrogen isotope distribution in 
nitrous oxide measured by isotope ratio mass spectrometry, 
Rapid.Commun. Mass Spectrom., 21, 391“405.
Unfortunatley, there ar no "official" standards for N2O until 
now.
Is there N2O production from Annamox? If so, then calibration 
of site-specific d15N would be crucial, since there would be 
different precursors (NH4+, NO3-) for the central and the two 
peripheral  N.
Hope this helps,
Reinhard




> Hello all,
> Our lab is beginning to measure N2O for annamox rates. As this is the
> first time I have gone down the N2O road, I was wondering if someone
> out there may be able to explain how N2O isotopic measurements are
> calibrated and calculated. I have heard rumor that one can use CO2 gas
> as the reference. Is this true? Any advice would be greatly
> appreciated. Thanks,
> 
> Brian Jones
> SCU
> NSW, AU


______________________________________
PD Dr. Reinhard Well
Institut für Bodenkunde und Waldernährung
Universität Göttingen
Büsgenweg 2
37077 Göttingen
Germany
phone +49 551 395507
fax +49 551 394619