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Removal of Nitrite Impurity from Nitrate Labeled with Nitrogen‐15
Author(s) -
Malone John P.,
Stevens R. James
Publication year - 1998
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/sssaj1998.03615995006200030015x
Subject(s) - nitrite , nitrate , impurity , chemistry , filtration (mathematics) , irradiation , nitrogen , tracer , potassium , catalysis , potassium nitrate , matrix (chemical analysis) , nuclear chemistry , chromatography , organic chemistry , physics , statistics , mathematics , nuclear physics
Potassium nitrate labeled with 15 N 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 K 15 NO 3 enriched to 99 atom % excess 15 N 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 TiO 2 catalyst. A NO − 2 concentration of 0.2 m M in 100 mL of 0.2 M NO − 3 solution could be oxidized in 12 min using 0.5 g L −1 TiO 2 in a specially constructed photoreactor with a 75‐W UV facial tanning lamp. For the routine removal of NO − 2 , use of the same TiO 2 concentration in a standard beaker worked equally well when the irradiation time was extended to 2.5 h. After irradiation, the TiO 2 is easily and totally removed from the solution by membrane filtration.