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This article in SSSAJ

  1. Vol. 62 No. 3, p. 651-653
     
    Received: May 9, 1996


    * Corresponding author(s): stevensj@dani.gov.uk
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doi:10.2136/sssaj1998.03615995006200030015x

Removal of Nitrite Impurity from Nitrate Labeled with Nitrogen-15

  1. John P. Malone and
  2. R. James Stevens 
  1. Agricultural and Environmental Science Dep., The Queen's Univ., Newforge Lane, Belfast BT9 5PX, UK
    Agricultural and Environmental Science Dep., The Queen's Univ., and Agricultural and Environmental Science Division, Dep. of Agriculture for Northern Ireland, Newforge Lane, Belfast BT9 5PX, UK

Abstract

Abstract

Potassium nitrate labeled with 15N is often used as a tracer in studies of N dynamics in soil and water systems. Typically, 0.8% NO2 impurity has been found in the batches of K15NO3 enriched to 99 atom % excess 15N that were purchased by our laboratory. Nitrite is an intermediate in several N cycling processes so its addition when adding NO3 could produce misleading results. We have developed a safe, simple, and inexpensive method to remove NO2 impurity from any NO3 solution in a water matrix. The principle is the oxidation of NO2 to NO3 by UV light in the presence of a heterogenous TiO2 catalyst. A NO2 concentration of 0.2 mM in 100 mL of 0.2 M NO3 solution could be oxidized in 12 min using 0.5 g L−1 TiO2 in a specially constructed photoreactor with a 75-W UV facial tanning lamp. For the routine removal of NO2, use of the same TiO2 concentration in a standard beaker worked equally well when the irradiation time was extended to 2.5 h. After irradiation, the TiO2 is easily and totally removed from the solution by membrane filtration.

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