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Automated Nitrogen‐15 Analysis of Ammonium in Diffusion Disks by the Rittenberg Technique
Author(s) -
Liu Y. P.,
Mulvaney R. L.
Publication year - 1992
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/sssaj1992.03615995005600040030x
Subject(s) - tray , diffusion , analytical chemistry (journal) , reagent , anhydrous , chemistry , liquid nitrogen , ammonium , nitrogen , chromatography , isotope dilution , mass spectrometry , materials science , mechanical engineering , physics , organic chemistry , engineering , thermodynamics
A recent development in 15 N analysis of inorganic N in soil extracts involves diffusion of NH 3 into acidified glass‐fiber disks in disposable specimen containers. A simple and convenient technique was developed for isotope‐ratio analysis of the NH 4 in these disks using a mass spectrometer equipped with an automated Rittenberg apparatus (ARA‐MS). For collection of diffused NH 3 , the disks were treated with 10 µL of 1 M H 2 SO 4 . Following diffusion for 6 d, the disks, containing 50 to 150 µg of N, were transferred to a disposable plastic sample tray (96 wells per tray) and treated with 10 µL of 28.9 M (concentrated) HF, which digested the disks without affecting the tray. The tray was placed in a desiccator containing anhydrous CaSO 4 , for drying of the digested disks in 1 to 3 d. Good agreement was obtained between 15 N analyses of diffused and nondiffused NH 4 ‐N when correction was made for isotopic dilution by NH 4 in the reagents used in diffusion. Trays containing the processed disks can be conveniently shipped to a service laboratory for analysis by ARA‐MS.