A suite of sensitive chemical methods to determine the δ15N of ammonium, nitrate and total dissolved N in soil extracts

Rapid Commun Mass Spectrom. 2010 Dec 30;24(24):3615-23. doi: 10.1002/rcm.4798.


Natural (15) N abundances (δ(15) N values) of different soil nitrogen pools deliver crucial information on the soil N cycle for the analysis of biogeochemical processes. Here we report on a complete suite of methods for sensitive δ(15) N analysis in soil extracts. A combined chemical reaction of vanadium(III) chloride (VCl(3) ) and sodium azide under acidic conditions is used to convert nitrate into N(2) O, which is subsequently analyzed by purge-and-trap isotope ratio mass spectrometry (PTIRMS) with a cryo-focusing unit. Coupled with preparation steps (microdiffusion for collection of ammonium, alkaline persulfate oxidation to convert total dissolved N (TDN) or ammonium into nitrate) this allows the determination of the δ(15) N values of nitrate, ammonium and total dissolved N (dissolved organic N, microbial biomass N) in soil extracts with the same basic protocol. The limits of quantification for δ(15) N analysis with a precision of 0.5‰ were 12.4 µM for ammonium, 23.7 µM for TDN, 16.5 µM for nitrate and 22.7 µM for nitrite.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chlorides / chemistry
  • Linear Models
  • Mass Spectrometry
  • Nitrates / chemistry*
  • Nitrites / chemistry
  • Nitrogen / analysis*
  • Nitrogen / chemistry
  • Nitrogen Isotopes / analysis*
  • Nitrogen Isotopes / chemistry
  • Nitrous Oxide / chemistry
  • Quaternary Ammonium Compounds / chemistry*
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Soil / analysis*
  • Time Factors
  • Vanadium Compounds / chemistry


  • Chlorides
  • Nitrates
  • Nitrites
  • Nitrogen Isotopes
  • Quaternary Ammonium Compounds
  • Soil
  • Vanadium Compounds
  • Nitrous Oxide
  • Nitrogen