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Application of liquid chromatography/electrospray ionization tandem mass spectrometry for the elucidation of hydroxyl radical oxidation of metsulfuron methyl and related sulfonylurea pesticide products: evidence for the triazine skeleton scission
Author(s) -
Chahboune Rajae,
Mountacer Hafida,
Sarakha Mohamed
Publication year - 2015
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.7234
Subject(s) - chemistry , electrospray ionization , hydroxyl radical , tandem mass spectrometry , hydroxylation , mass spectrometry , demethylation , radical , bond cleavage , sulfonylurea , photochemistry , organic chemistry , chromatography , medicine , biochemistry , gene expression , endocrinology , insulin , dna methylation , gene , enzyme , catalysis
Rationale Sulfonylureas are among the most important class of antidiabetic and herbicides. Solar light excitation and Advanced Oxidation Processes may result in the formation of a wide array of products owing to the relative complex structure. These products, that should be identified, may present a more toxic effect than the parent compound. Methods Liquid chromatography/electrospray ionization quadrupole time‐of‐flight mass spectrometry (LC/ESI‐QTOFMS) with accurate mass determination emerges as a valuable technique for the precise elucidation of all possible byproducts. The hydroxyl radical was generated by excitation of the iron(III) aquacomplex [Fe(H 2 O)OH] 2+ and hydrogen peroxide at pH 3.5. Three different sulfonylureas were studied: metsulfuron methyl, cinosulfuron and thifensulfuron methyl. Results Several products owing to the reactivity of hydroxyl radicals with sulfonylurea were obtained. They arise from scission of the sulfonylurea bridge, hydroxylation of the aromatic ring, demethylation of the methoxy group and more importantly and unequivocally from the rupture of the triazine skeleton. To reach such scission, a primary demethylation of the methoxy group on the triazine moiety seems to act as a precursor process. Such a process was observed with the three studied sulfonylurea compounds. Conclusions The reported results demonstrated the usefulness of accurate mass measurements undertaken by LC/ESI‐QTOFMS for structural elucidation of the unknown byproducts that were generated during hydroxyl radical reactions with some sulfonylureas. It has been possible herein to identify the structures of products arising from the opening of the recalcitrant triazine structure via hydrolysis processes in acidic solutions. Copyright © 2015 John Wiley & Sons, Ltd.