A suite of sensitive chemical methods to determine the ?15N of ammonium, nitrate and total dissolved N in soil extracts. Academic Article uri icon


  • Natural (15) N abundances (?(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 ?(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 ?(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 ?(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 date

  • December 30, 2010