title: Abiotic degradation of iodosulfuron-methyl-ester in aqueous solution.
abstract: The abiotic degradation of iodosulfuron-methyl-ester was investigated under both alkaline and acidic pH conditions in the dark, and results showed it to be a rather stable molecule in neutral or slightly alkaline environments. Photochemical reactions were studied using a high-pressure mercury arc lamp, and results showed that direct phototransformation is possible under normal environmental conditions (lambda > 290 nm). High-performance liquid chromatography (HPLC-UV and HPLC-MS) analyses were used to identify the degradates and to study the kinetics of photodecomposition and hydrolysis. Five main products of iodosulfuron-methyl-ester degradation were tentatively identified, and one of them (4-methoxy-6-methyl-1,3,5-triazin-2-amine) was confirmed using an authentic standard. Among the phototransformation mechanisms, photosubstitution of the iodide atom by a hydroxyl group, photodissociation of the N-S bond, and photoassisted hydrolysis were observed. The quantum efficiencies (multiwavelength quantum yield) of the photodegradation under different conditions were determined, and values of 0.054 +/- 0.02 (pH 9.6), 0.08 +/- 0.02 (pH 7), and 0.044 +/- 0.008 (pH 5.3) were obtained.
authors.affiliation: Laboratoire d'Application de la Chimie à l'environnement (L.a.c.E), UMR CNRS 5634, Université Lyon ,Villeurbanne, France.
authors.forename: M
authors.initials: M
authors.lastname: Brigante
authors.forename: C
authors.initials: C
authors.lastname: Emmelin
authors.forename: L
authors.initials: L
authors.lastname: Previtera
authors.forename: R
authors.initials: R
authors.lastname: Baudot
authors.forename: J M
authors.initials: JM
authors.lastname: Chovelon
mesh_terms: D002851:Chromatography, High Pressure Liquid; D004952:Esters / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D013058:Mass Spectrometry; D008745:Methylation; D010777:Photochemistry; D012996:Solutions; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry; D013449:Sulfonamides / Q000737:chemistry*; D014867:Water
chemical_list: D004952:Esters; D012996:Solutions; D013449:Sulfonamides; D014867:Water; C474738:iodosulfuron