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Combined Microdiffusion‐Hypobromite Oxidation Method for Determining Nitrogen‐15 Isotope in Ammonium
Author(s) -
RisgaardPetersen Nils,
Revsbech Niels Peter,
Rysgaard Søren
Publication year - 1995
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1995.03615995005900040018x
Subject(s) - chemistry , ammonium , isotope , nitrogen , mass spectrometry , analytical chemistry (journal) , inorganic chemistry , chromatography , organic chemistry , physics , quantum mechanics
A limiting factor for work with biological N transformations has been unsatisfactory procedures for analysis of 15 N isotope labeling in small amounts of NH + 4 . Using the procedure described here, it is now possible to perform accurate determinations in NH + 4 pools as small as 2 nmol. By diffusion of NH 3 through a gas phase, N in NH + 4 is transferred from the sample and into a hypobromite solution, where an oxidation to N 2 occurs. The N 2 originating from the oxidation is mixed with N 2 initially dissolved in the sample, which functions as a carrier during subsequent mass spectrometry. Random isotopic pairing of the N atoms originating from NH 3 oxidation makes it possible to calculate the original 15 N abundance in the NH + 4 pool from the relative amounts of 14 N 15 N and 15 N 15 N in the reaction container. The combined microdiffusion‐hypobromite oxidation method for 15 NH + 4 analysis proved to be very precise (standard error <0.15 atom %, n = 5) when applied on samples with an 15 N enrichment >1 atom %, and interference was found only for volatile methyl amines.