Removal of Nitrite Impurity from Nitrate Labeled with Nitrogen-15
- John P. Malone and
- R. James Stevens
Potassium nitrate labeled with 15N is often used as a tracer in studies of N dynamics in soil and water systems. Typically, 0.8% NO−2 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 NO−3 could produce misleading results. We have developed a safe, simple, and inexpensive method to remove NO−2 impurity from any NO−3 solution in a water matrix. The principle is the oxidation of NO−2 to NO−3 by UV light in the presence of a heterogenous TiO2 catalyst. A NO−2 concentration of 0.2 mM in 100 mL of 0.2 M NO−3 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 NO−2, 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.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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