Unequivocal Identification of Compounds Formed in the Photodegradation of Fenitrothion in Water/Methanol and Proposal of Selected Transformation Pathways

• Published in: Journal of agricultural and food chemistry Vol. 42; no. 3; pp. 814 - 821
• Main Authors: Durand, G, Abad, J. L, Sanchez-Baeza, F, Messeguer, A, Barcelo, D
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 01.03.1994; Amer Chemical Soc
• Subjects: Agriculture; Agriculture, Multidisciplinary; Analysis methods; Applied sciences; Chemistry; Chemistry, Applied; Exact sciences and technology; Food Science & Technology; Life Sciences & Biomedicine; Natural water pollution; Physical Sciences; Pollution; Science & Technology; Water treatment and pollution; CHROMATOGRAPHY MASS-SPECTROMETRY; PHOSPHORUS; CHEMICAL IONIZATION; GAS-CHROMATOGRAPHY; PHOSPHOROTHIOATES; ORGANOPHOSPHORUS PESTICIDES; PHOTOCHEMISTRY; PHOTOLYSIS; DEGRADATION PRODUCTS; PARATHION; Degradation; Water; Insecticide; Ultraviolet irradiation; Photolysis; Reaction mechanism; Organophosphorus compounds; Water pollution; Methanol
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf00039a044

The photodegradation of fenitrothion was examined in a mixture of distilled water/methanol (5:1), The UV irradiation was carried out with a high-pressure Hg lamp during 7 h. For the identification of further breakdown products, fenitrooxon and carboxyfenitrothion were also irradiated under experimental conditions identical to those for fenitrothion. The identification of the breakdown products formed was carried out by gas chromatography-mass spectrometry (GC-MS) with electron impact (EI) and comparison with authentic standards synthesized in the laboratory. A total of 21 photoproducts of oxidation, isomerization, denitration, and solvolysis that may be of concern in environmental studies were unequivocally identified. Among them were formyldenitrofenitrothion, carbomethoxydenitro-fenitrooxon, and hydroxymethyldenitrofenitrooxon. A proposed mechanism of the process is presented. Selected pathways for the photodegradation of fenitrothion were examined: (i) degradation through hydrolysis, with eventual remethylation; (ii) P=S to P=O oxidation; (iii) denitration; and (iv) oxidation of the methyl substituent through hydroxymethyl and formyl to give the corresponding carboxy derivatives.