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This article in SSSAJ

  1. Vol. 56 No. 4, p. 1185-1188
    Received: Aug 27, 1991

    * Corresponding author(s):
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Automated Nitrogen-15 Analysis of Ammonium in Diffusion Disks by the Rittenberg Technique

  1. Y. P. Liu and
  2. R. L. Mulvaney 
  1. Dep. of Agronomy, 1102 S. Goodwin Ave., Univ. of Illinois, Urbana, IL 61801



A recent development in 15N analysis of inorganic N in soil extracts involves diffusion of NH3 into acidified glass-fiber disks in disposable specimen containers. A simple and convenient technique was developed for isotope-ratio analysis of the NH4 in these disks using a mass spectrometer equipped with an automated Rittenberg apparatus (ARA-MS). For collection of diffused NH3, the disks were treated with 10 µL of 1 M H2SO4. 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 CaSO4, for drying of the digested disks in 1 to 3 d. Good agreement was obtained between 15N analyses of diffused and nondiffused NH4-N when correction was made for isotopic dilution by NH4 in the reagents used in diffusion. Trays containing the processed disks can be conveniently shipped to a service laboratory for analysis by ARA-MS.

This study was a part of Project ILLU-15-0392, Illinois Agric. Exp. Stn.

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