Study of alloxydim photodegradation in the presence of natural substances: Elucidation of transformation products

• Published in: Journal of photochemistry and photobiology. A, Chemistry. Vol. 198; no. 2; pp. 162 - 168
• Main Authors: Sevilla-Morán, Beatriz, Sandín-España, Pilar, Vicente-Arana, M. Jesús, Alonso-Prados, José L., García-Baudín, José M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.08.2008
• Subjects: Alloxydim; Aqueous solution; Natural substances; Photodegradation; Time-of-flight mass analyser; Photodegradation; Natural substances; Time-of-flight mass analyser; Aqueous solution; Alloxydim
• ISSN: 1010-6030; 1873-2666
• DOI: 10.1016/j.jphotochem.2008.03.005

A photodegradation study of alloxydim was performed under simulate solar irradiation (Suntest apparatus) at different irradiation intensities. Moreover, indirect photolysis of the tested herbicide was investigated under the presence of various concentrations of humic acids (HA), nitrate and Fe (III) ions. The photodegradation of alloxydim follows a first-order reaction kinetics in all cases. HA inhibited the photolysis kinetic whereas rate constants measured in the presence of nitrate ions indicated no effect on degradation. On the contrary, Fe (III) ions enhanced the photodegradation rate of alloxydim. Kinetics experiments were monitored by HPLC–DAD and the half-lives ranged from 165.78 to 4.63 min for different intensities in direct photolysis and from 104.81 to 1.14 min for indirect photolysis. The study of transformation products have been investigated by HPLC coupled to quadrupole time-of-flight mass spectrometry (QTOF-MS) employing the electrospray technique. The most important transformation process was found to be the cleavage of the O–N bond of the oxime moiety. Minor photo-isomerization to Z-isomer was also observed. The appearance of these degradation products is reported in aqueous media for the first time.