Photodegradation of the herbicide penoxsulam in aqueous methanol and acetonitrile

• Published in: Journal of environmental science and health. Part B, Pesticides, food contaminants, and agricultural wastes Pesticides, food contaminants, and agricultural wastes, 2008-09, Vol.43 (7), p.569-575
• Main Authors: Pramanik, Sukhendu K, Das, Saktipada, Bhattacharyya, Anjan
• Format: Article
• Language: English
• Subjects: acetonitrile; Acetonitriles - chemistry; Agronomy. Soil science and plant productions; aqueous solutions; Biological and medical sciences; byproducts; Freshwater; Fundamental and applied biological sciences. Psychology; herbicides; Herbicides - chemistry; Kinetics; methanol; Methanol - chemistry; Oryza sativa; Oxidation-Reduction; Penoxsulam; Photochemistry; photolysis; photoproduct; reaction kinetics; Soil and water pollution; Soil science; solar radiation; solvents; Sulfonamides - chemistry; sunlight; Titanium - chemistry; titanium dioxide; ultraviolet radiation; Ultraviolet Rays; Uridine - analogs & derivatives; Uridine - chemistry; UV light; Water - chemistry; water pollution
• ISSN: 0360-1234; 1532-4109
• DOI: 10.1080/03601230802234427

Penoxsulam is a triazolopyrimidine sulfonamide group of rice herbicide. The phototransformation of penoxsulam was studied under UV light (λ max ≥ 290 nm) and sunlight in aqueous methanol and acetonitrile solvent system using TiO 2 as sensitizer. The rate of photodegradation of penoxsulam in different solvent systems followed first-order kinetics and calculated half-lives was found to be in the range of 51.89-73.41 h and 62.70-97.09 h for UV light and sunlight respectively in the presence or absence of sensitizer. From this study, a total of six photoproducts were identified and characterized on the basis of Q-Tof micromass spectral data. The plausible mechanism of phototransformation involved were hydrolysis, photo oxidation of the sulfonamide group, breaking of sulfonamide bond, loss of amino and sulfonic acid group.