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A method for nitrite removal in nitrate N and O isotope analyses
Author(s) -
Granger Julie,
Sigman Daniel M.,
Prokopenko Maria G.,
Lehmann Moritz F.,
Tortell Philippe D.
Publication year - 2006
Publication title -
limnology and oceanography: methods
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.898
H-Index - 72
ISSN - 1541-5856
DOI - 10.4319/lom.2006.4.205
Subject(s) - nitrite , nitrate , chemistry , ascorbic acid , nitrogen , denitrification , environmental chemistry , seawater , inorganic chemistry , nitric acid , organic chemistry , ecology , food science , biology
We describe a method to remove nitrite from seawater and freshwater samples to determine the nitrogen (N) and oxygen (O) isotopic composition of nitrate in aqueous samples ( 15 N/ 14 N and 18 O/ 16 O, respectively). This method is simple, inexpensive, and effective in the removal of nitrite without compromising the natural N and O isotopic composition of nitrate. Moreover, the method is nontoxic and compatible with the “denitrifier method” for nitrate N and O isotope analysis. Nitrite is removed from solution by reduction to nitric oxide (NO) gas using ascorbic acid at a pH of ~3.5. The NO produced is continually degassed with an inert gas during the reaction, preventing O 2 from reacting with NO to form new nitrate. Nitrate N and O isotope ratios were measured with the denitrifier method. The precision of isotope measurements of nitrate by the denitrifier method after nitrite removal averaged ±0.34‰ for 15 N/ 14 N and ±0.39‰ for 18 O/ 16 O.