Structural Elucidation of Sulfaquinoxaline Metabolism
Products and Their Occurrence in Biological Samples Using High-Resolution
Orbitrap Mass Spectrometry
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Abstract
Four
previously unreported metabolism products of sulfaquinoxaline
(SQX), a widely used veterinary medicine, were isolated and analyzed
using liquid chromatography coupled to high-resolution Orbitrap mass
spectrometry. Metabolites were structurally elucidated, and a fragmentation
pathway was proposed. The combination of high-resolution MS<sup>2</sup> spectra, linear ion trap MS<sup>2</sup>, in-source collision-induced
dissociation (CID) fragmentation, and photolysis were used to analyze
SQX and its metabolites. All metabolism products identified showed
a similar fragmentation pattern to that of the original drug. Differential
product ions were produced at <i>m</i>/<i>z</i> 162 and 253 which contain the radical moiety with more 16 Da units
than sulfaquinoxaline. This occurs by a hydroxyl attachment to the
quinoxaline moiety. With the exception of two low-intensity compounds,
all the mass errors were below 5.0 ppm. The distribution of these
metabolites in some animal species are also presented and discussed