Photocatalytic degradation of phenyl-urea herbicides chlortoluron and chloroxuron: characterization of the by-products by liquid chromatography coupled to electrospray ionization tandem mass spectrometry.
The first stages of the photocatalytic degradation of the compounds chlortoluron [3-(3-chloro-4-methylphenyl)-1,1-dimethylurea] and chloroxuron [3-[4-(4-chlorophenoxy)phenyl]-1,1-dimethylurea], belonging to the class of phenyl-urea herbicides, were investigated using high-performance liquid chromatography (HPLC) coupled to electrospray ionization ion trap tandem mass spectrometry (ESI-IT-MS/MS). Degradation was accomplished under solar radiation, using TiO2 embedded into a polyvinylidene fluoride (PVDF) transparent matrix as a heterogeneous photocatalyst. Aliquots of the chlorinated herbicide solutions were withdrawn at different times and subjected to gradient elution, reversed-phase HPLC separations, specifically optimized to obtain the highest resolution between peaks related to the herbicide degradation by-products. The latter were then investigated using MS detection; in particular, MS/MS measurements were made and structural information was obtained from the interpretation of fragmentation data. Several by-products were identified; the most important ones are hydroxylated compounds arising from the interaction between the two chlorinated herbicides and OH radicals generated at the TiO2 surface under irradiation. Other by-products were generated by slightly different processes, namely demethylation, dearylation and dechlorination, eventually followed by interaction with OH radicals.
Amorisco
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A
Università degli Studi di Bari, Dipartimento di Chimica, Via E. Orabona 4, 70126 Bari, Italy.
Losito
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Carbonara
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Palmisano
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Zambonin
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PG
D002384:Catalysis; D002713:Chlorine / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D006540:Herbicides / Q000737:chemistry*; D008782:Methylurea Compounds / Q000737:chemistry*; D010671:Phenylurea Compounds / Q000737:chemistry*; D010777:Photochemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D013056:Spectrophotometry, Ultraviolet; D014025:Titanium / Q000737:chemistry
D006540:Herbicides; D008782:Methylurea Compounds; D010671:Phenylurea Compounds; C009495:titanium dioxide; D002713:Chlorine; D014025:Titanium; C012829:chloroxuron; C007033:chlortoluron