Photodegradation of Hexythiazox in Different Solvent Systems under the Influence of Ultraviolet Light and Sunlight in the Presence of TiO₂, H₂O₂, and KNO₃ and Identification of the Photometabolites

Abstract

The photodegradation of the carboxamide acaricide hexythiazox in three different solvent systems (aqueous methanolic, aqueous isopropanolic, and aqueous acetonitrilic solutions) in the presence of H(2)O(2), KNO(3), and TiO(2) under ultraviolet (UV) light (λ(max) ≥ 250 nm) and sunlight (λ(max) ≥290 nm) has been assessed in this work. The kinetics of photodecomposition of hexythiazox and the identification of photoproducts were carried out using liquid chromatography-mass spectrometry. The rate of photodecomposition of hexythiazox in different solvents followed first-order kinetics in both UV radiation and natural sunlight, and the degradation rates were faster under UV light than under sunlight. Hexythiazox was found to be more efficiently photodegraded in the presence of TiO(2) than in the presence of H(2)O(2) and KNO(3). Two major photoproducts were separated in pure form using column chromatography and identified according to IR, (1)H NMR, and mass spectral information as cyclohexylamine and 5-(4-chlorophenyl)-4-methylthiazolidin-2-one. Another nine photoproducts were identified according to LC-MS/MS spectral information. The plausible photodegradation pathways of hexythiazox were proposed according to the structures of the photoproducts.

Photodegradation of Oryzalin in aqueous isopropanol and acetonitrile

“…The sunlight photolysis, is highly dependent not only on the UV absorption profile of the pesticides but also on the surroundings medium and the emission spectrum of the sunlight. [1] Mandal, S.; Joardar, S.; Das, S.; Bhattacharyya, A. Photodegradation of hexythiazox in different solvent systems under the influence of ultraviolet light and sunlight in the presence of TiO2, H2O2 and KNO3 and identification of the photoproducts. J. Agric.…”

Hydrolysis and Photolysis of Herbicide Clomazone in Aqueous Solutions and Natural Water Under Abiotic Conditions

“…Thus, the degradation study of pesticides has become increasingly important in recent years (Lin et al, 2011). Residual pesticides are known to be decomposed by various natural conditions in which hydrolysis and photodegradation are the most important factors involved in the decomposition of pesticides in the environment (Mandal et al, 2011;Chamberlain et al, 2012). In the surface layers of aquatic systems, photochemical reactions can play an important role in the degradation of herbicides，so photochemical studies in aqueous solution to assess the fate of herbicides over a wide range of environmental conditions should be taken into account (Da Silva et al, 2003).…”

Photolysis by UVA–Visible Light of TNT in Ethanolic, Aqueous-Ethanolic, and Aqueous Solutions According to Electrospray and Aerodynamic Thermal Breakup Droplet Ionization Mass Spectrometry

“…The solvent behaves as an electron donor, and the pesticide behaves as an electron acceptor. The degradation pathway and the end products of photolysis depend on the type of solvent in many other cases [16][17][18].…”