title: Effect of positional isomerism on the abiotic degradation of pesticides: Case of m- and p-imazamethabenz-methyl.
abstract: The effect of positional isomerism on chemical and photochemical degradations of the Imazamethabenz-methyl (IMBM), a pesticide of the imidazolinone family, has been studied. IMBM is proposed in the form of a mixture of the two positional isomers: meta and para. The development of an effective HPLC method (resolution factor R=1.3) allows us to follow either the abiotic disappearance of the meta and para IMBM and the formation of their breakdown products. The abiotic degradation studies include the chemical hydrolysis, as well as the direct and the indirect photodecomposition. We used TiO(2), a well-known initiator of hydroxyl radicals, to highlight the role of *OH in the indirect photodegradation. This work confirms the different behaviours of positional isomers in the environment. Indeed the chemical or direct photochemical degradation is faster for the meta isomer than for the para. Whereas, concerning IMBM, there is not any prevalent influence of this type of isomerism on the indirect photochemical degradation. The degradation products were tentatively identified by LC-MS, NMR and IR and a degradation pathway was proposed.
authors.affiliation: IRCELYON, Institut de Recherches sur la Catalyse et l'Environnement de Lyon, 2 avenue Albert Einstein, UMR5256, CNRS - Université Claude Bernard Lyon 1, Villeurbanne, F-69626 cedex, France.
authors.forename: Marcello
authors.initials: M
authors.lastname: Brigante
authors.forename: Corinne
authors.initials: C
authors.lastname: Emmelin
authors.forename: Corinne
authors.initials: C
authors.lastname: Ferronato
authors.forename: Marina Della
authors.initials: MD
authors.lastname: Greca
authors.forename: Lucio
authors.initials: L
authors.lastname: Previtera
authors.forename: Jean Olivier
authors.initials: JO
authors.lastname: Paisse
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Chovelon
mesh_terms: D001565:Benzoates / Q000737:chemistry*; D006540:Herbicides / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry*; D008027:Light; D015394:Molecular Structure; D013997:Time Factors
chemical_list: D001565:Benzoates; D006540:Herbicides; D007093:Imidazoles; C521119:m-imazamethabenz-methyl; C521118:p-imazamethabenz-methyl