Degradation intermediates and reaction pathway of pyraclostrobin with TiO2 photocatalysis

L. Lagunas-Allue (1) , M. T. Martinez-Soria , J. Sanz-Asensio , A. Salvador , C. Ferronato (2) , J. M. Chovelon (1)

1 EAU - EAU
2 AIR:EAU+CFE

The present study deals with the photocatalytic degradation of the strobilurin pyraclostrobin in the presence of titanium dioxide (TiO2) as a photocatalyst and UV light irradiation. The obtained results show a complete degradation of pyraclostrobin at pH 6.2, temperature at 20 +/- 1 degrees C and 0.5 g L-1 of catalyst after 60 min irradiation. Photodegradation of pyraclostrobin exhibited pseudo-first-order reaction kinetics. The rate of photodecomposition of pyraclostrobin was measured using high performance liquid chromatography-diode array detector (HPLC-DAD). The effect of solution pH in the 2-10 range was investigated as well as the reaction intermediates formed during degradation. To obtain a better understanding of the mechanistic details of this TiO2-assisted photodegradation of pyraclostrobin with UV-irradiation, the intermediates of the processes were concentrated, separated and identified by the solid-phase extraction (SPE) and liquid chromatography/mass spectrometry (LC-MS/MS) technique. The probable photodegradation pathways were proposed and discussed. The main steps involved: hydroxylation of the aromatic rings (chloro-phenyl, phenyl and pyrazol) followed by the loss of the N-methoxy group, substitution of chloride atom by a hydroxyl group, rupture of the pyrazol and phenyl bond and the scission of the oxygen and pyrazol bond. (C) 2011 Elsevier B.V. All rights reserved.

Domaines: Catalyse; Environnement et Société

L. Lagunas-Allue, M. T. Martinez-Soria, J. Sanz-Asensio, A. Salvador, C. Ferronato, et al.. Degradation intermediates and reaction pathway of pyraclostrobin with TiO2 photocatalysis. Applied Catalysis B: Environmental, 2012, 115, pp.285-293. ⟨10.1016/j.apcatb.2011.12.015⟩. ⟨hal-00700187⟩