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Liquid chromatography/electrospray ionization quadrupole time-of-flight mass spectrometry for the analysis of sulfaquinoxaline byproducts formed in water upon solar light irradiation.
MedLine Citation:
PMID:  23418152     Owner:  NLM     Status:  In-Data-Review    
Abstract/OtherAbstract:
RATIONALE: Sulfonamides such as sulfaquinoxaline (SQX) are among the most important antibiotic families due to their extensive use in veterinary medicine. The prediction of their fate under solar irradiation through the identification of the generated metabolites is required. However, unambiguous structural characterizations often remain a challenge particularly when several isomers could match with the same MS(2) data.
METHODS: Liquid chromatography/electrospray ionization quadrupole time-of-flight mass spectrometry (LC/ESI-Q-TOFMS) in the positive ion mode, leading to the formation of the protonated forms of the studied compounds, [M + H(+) ] ions, was employed. Collision-induced dissociation tandem mass spectrometry (CID-MS/MS) of the protonated molecules was carried out, and the effect of the collision energy as well as the elemental compositions of the product ions were used to propose chemical structures. Validation of the hypothesized structures was performed by the calculation of key fragmentation pathway energies using density functional theory (DFT) calculations (B3LYP/6-31 G (d,p)).
RESULTS: The photoproducts were identified as 2-aminoquinoxaline, SQX isomers, 2-(N-parabenzoquinoneimine)quinoxaline and isomers resulting from SO(2) extrusion. The direct fragmentations of [SQX + H](+) and its protonated isomers mostly occurred through the loss of 2-aminoquinoxaline and/or the 4-sulfoaniline radical ion, while their rearrangements involved the migration of H and/or O atoms. For the desulfonated byproducts in their protonated forms, the main neutral losses were of the quinoxaline radical, aminoquinoxaline and NH(3) . The fragmentation of the protonated 2-aminoquinoxaline mainly involved the elimination of NH(3) and HCN.
CONCLUSIONS: LC/ESI-Q-TOFMS and DFT calculations have been shown to be useful and complementary methods for the identification of unknown isomeric compounds and the elucidation of fragmentation patterns, in the case of the sulfaquinoxaline veterinary antibiotic. Copyright © 2013 John Wiley & Sons, Ltd.
Authors:
C Le Fur; B Legeret; P de Sainte Claire; P Wong-Wah-Chung; M Sarakha
Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Rapid communications in mass spectrometry : RCM     Volume:  27     ISSN:  1097-0231     ISO Abbreviation:  Rapid Commun. Mass Spectrom.     Publication Date:  2013 Mar 
Date Detail:
Created Date:  2013-02-18     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8802365     Medline TA:  Rapid Commun Mass Spectrom     Country:  England    
Other Details:
Languages:  eng     Pagination:  722-30     Citation Subset:  IM    
Copyright Information:
Copyright © 2013 John Wiley & Sons, Ltd.
Affiliation:
Clermont Université, Université Blaise Pascal, Institut de Chimie de Clermont Ferrand (ICCF), BP 80026, F-63171, Aubière, France; CNRS, UMR 6296, Institut de Chimie de Clermont Ferrand (ICCF), Photochimie, BP 80026, F-63171, Aubière, France.
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