Photodegradation of diafenthiuron in water

Abstract

Diafenthiuron, 1-tert-butyl-3-(2,6-di-isopropyl-4-phenoxyphenyl)thiourea, is an effective insecticide and acaricide. Sunlight degradation of diafenthiuron in various aqueous solutions and pure hexane yielded two major identified products: 1-tert-butyl-3-(2,6-di-isopropyl-4-phenoxyphenyl)-carbodiimide (CGA-140,408) and 1-tert-butyl-3-(2,6-di-isopropyl-4-phenoxy-phenyl)urea (CGA-177,960). CGA-140,408 was further photo-transformed into CGA-177,960 by sunlight. Direct photolysis appeared to be a major photolysis pathway of diafenthiuron in the environment. Photodegradation of CGA-140,408 and CGA-177,960 was enhanced in humic acid water, paddy water and aqueous acetone solutions, and followed first-order kinetics. Isopropanol (a radical quencher) and de-aeration strongly inhibited the photolysis of these chemicals, which suggested oxygen radical-mediated reactions.

Hydrolysis and photolysis of paroxetine, a selective serotonin reuptake inhibitor, in aqueous solutions

“…Like hydrolysis in buffer solutions, no hydrolysis was observed in synthetic humic water and lake waters in the dark. In general, humic substances are known to be sensitizers in photoreactions of organic chemicals via the generation of various active oxygen species [13][14][15][16][17][18][19]. These photosensitized reactions can result in accelerated photodegradation of compounds that are stable to sunlight in distilled water.…”

“…Chemicals that cannot absorb light above 290 nm are resistant to direct photodegradation; however, there are many oxidants and reductants capable of accelerating photodegradation in the environment. Examples of such oxidants are hydroxyl radical, singlet oxygen, carbonate radical, humic acid, and fulvic acid [13][14][15][16][17][18][19][20][21][22][23][24].…”

Toxicity of diafenthiuron to honey bees in laboratory, semi-field and field conditions

“…Diafenthiuron showed complex metabolism in apple, tomato and cotton, and it also exhibits strong translaminar and vapour activity (http://www.agtech.com). It degrades very rapidly in Chinese cabbage, and was found to accumulate as a metabolite in the inner tissues 31. Diafenthiuron is a proinsecticide, and the degradation product is a urea derivative, resulting in phytotonic effects in plants (http://www.syngenta.co.th/pegasus.pdf), so the assessment of diafenthiuron on honey bees in the field is inevitable.…”

High-Throughput Screening System for Identifying Phototoxic Potential of Drug Candidates Based on Derivatives of Reactive Oxygen Metabolites

“…For instance, dimethyl sulfoxide and isopropanol were found to act as quenchers of some reactive oxidants (27,28), whereas hexane and deuterium monoxide might stabilize some radical species with an extension of the half-life time (29,30). In our previous study, the use of acetonitrile-containing buffer was proposed for the ROS assay, because of its only slight influence on determination of singlet oxygen and superoxide (14).…”