ANALYTICAL AND MECHANISTIC ASPECTS OF THE POLAROGRAPHIC-REDUCTION OF THE HERBICIDE PYRAZON

This article describes a study of the polarographic reduction of the herbicide pyrazon, which yields two polarographic reduction waves: one in acidic media and the other in alkaline media. Coulometric data indicate the exchange of two electrons per molecule, while infrared spectroscopic data reveal that the reduction process involves the azomethine (>CN) rather than the carbonyl group or the NN bond. A mechanism for the electrode reaction is postulated, and a pulse polarographic method for the quantitative determination of pyrazon is proposed. The detection limit achieved by differential pulse polarography in a 1.0 M sulfuric medium is 7 × 10−8 M (0.015 ppm). Copyright © 1990 VCH Publishers, Inc.