Problem of concurrent measurements of peroxonitrite and nitrite contents

Abstract

It has been thought that metastable peroxonitrite, ONOO^–, does not interfere with the determination of nitrite, NO₂^–, because of evidence that it decays by isomerization to NO₃^–. In fact, the isomerization process is quantitative only under acidic conditions; partial decomposition to NO₂^– can take place in neutral solutions and quantitative decomposition to NO₂^– can occur in basic media with a metal catalyst. A method of analysis of these systems, based on these findings, is described. The details of the solution behaviour of ONOO^– have not been recognized in the 50 years of studies of the photochemistry of nitrates where both NO₂^– and ONOO^– are produced. As a result analyses were in error and changes in concentration of ONOO^– with experimental variables have frequently appeared as changes in NO₂^– content, which were theoretically inexplicable.