Photolysis of oxyfluorfen in aqueous methanol

Abstract

Photolysis of oxyfluorfen, an herbicide of the nitrodiphenyl ether class, was studied in aqueous methanol under UV and sunlight. UV irradiation was carried out in a borosilicate glass photoreactor (containing 250 ppm oxyfluorfen in 50% aqueous methanol) equipped with a quartz filter and 125 watt mercury lamp (maximum output 254 nm) at 25 ± 1°C. Sunlight irradiation was conducted at 28 ± 1°C in borosilicate Erlenmeyer flasks containing 250 ppm oxyfluorfen in 50% aqueous methanol. The samples from both the irradiated conditions were withdrawn at a definite time interval and extracted to measure oxyfluorfen content by gas chromatography-flame ionization detector for rate study. The half-life values were 20 hours and 2.7 days under UV and sunlight exposure, respectively. Photolysis of oxyfluorfen yielded 13 photoproducts of which three were characterized by infrared spectrophotometer and (1)H NMR and (13)C NMR spectroscopy. The rest of the photoproducts were identified by gas chromatography-mass spectrometry (GC-MS) and thin layer chromatography (TLC). An ionization potential 70 eV was used for electron impact-mass spectrometry (EI-MS) and methane was used as reagent gas for chemical ionization-mass spectrometry (CI-MS). Two of the photoproducts were also synthesized for comparison. The main phototransformation pathways of oxyfluorfen involved nitro reduction, dechlorination, and hydrolysis as well as nucleophiles displacement reaction.

A Review of Remediation Strategies for Diphenyl Ether Herbicide Contamination

“…There is very little research on the photodegradation remediation process of diphenyl ether compounds. Chakraborty et al [ 77 ] reported that the photodegradation products of oxyfluorfen may undergo ether bond cleavage and dehalogenation pathways. In the process of using TiO 2 to degrade acifluorfen, Xin [ 71 ] also confirmed the cleavage of ether bonds, dehalogenation, hydroxylation, and other products.…”

Review of advances in the thin layer chromatography of pesticides: 2012–2014

“…The main transformation pathways of oxyfluorfen involved nitro reduction, dechlorination, hydrolysis, and nucleophile displacement reaction. [65] Interaction between Cd C2 and the insecticide CPF in inducing hepatoxicity was studied by allowing 0.01-M solutions of each to react in ethyl acetate or deionized water under slow mixing for 24 h. The mixture was analyzed by TLC on silica gel plates developed with ethyl acetate-hexane (30:70) followed by visualization by exposure to iodine and viewing under UV light. It was demonstrated that joint hepatoxicity of Cd ion and CPF was chiefly due to the Cd-CPF complex-facilitated intercellular transport associated with oxidative stress under environmental and biological settings, posing substantial health risk by cooccurrence to humans.…”