A suite of sensitive chemical methods to determine the delta N-15 of ammonium, nitrate and total dissolved N in soil extracts

作者：Lachouani Petra; Frank Alexander H; Wanek Wolfgang^*

来源：Rapid Communications in Mass Spectrometry, 2010, 24(24): 3615-3623.

DOI：10.1002/rcm.4798

Natural N-15 abundances (delta N-15 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 delta N-15 analysis in soil extracts. A combined chemical reaction of vanadium(III) chloride (VCl3) and sodium azide under acidic conditions is used to convert nitrate into N2O, 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 delta N-15 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 delta N-15 analysis with a precision of 0.5% were 12.4 mu M for ammonium, 23.7 mu M for TDN, 16.5 mu M for nitrate and 22.7 mu M for nitrite.

• 出版日期2010-12