US Patent 4,412,006
United States Patent and Trademark Office
University of Iowa Research Foundation (Iowa City, IA, US)
A technique of determination of nitrate-nitrite content of a test sample, without also determining additional nitrogen content. The technique is highly selective and sensitive, to the parts per billion level. The nitrate-nitrite content of a sample is reduced to nitric oxide which is determined via its chemiluminescence reaction with ozone. Nitrite is selectively reduced under mild conditions and the total nitrate-nitrite content is determined by stronger reduction conditions. Specific reducing agents to be used in combination with the chemiluminescence reaction are also provided.
Cox, Robert D. and Frank, Clyde W. Method for determination of nitrate and/or nitrite. US Patent 4,412,006 filed March 25, 1982 and issued October 25, 1983. https://ir.uiowa.edu/patents/34