A groundbreaking new paper from Altabet et al.* has described a new technique for the conversion of dissolved nitrate to N2O without using hazardous reagents or bacterial cultures giving fully prepared samples within 24 hours. With easily obtained reagents and basic laboratory infrastructure, novice labs can perform high quality isotopic analysis of nitrate.
* Altabet, M.A., Wassenaar, L.I., Douence, C., Roy, R. (2019) A Ti(III) reduction method for one-step conversion of seawater and freshwater nitrate into N2O for stable isotopic analysis of 15N/14N, 18O/16O and 17O/16O, Rapid Communications in Mass Spectrometry, Vol 33, Issue 15, Pages 1227-1239. Link: https://doi.org/10.1002/rcm.8454