Fig. 4: Stable isotope-assisted unexpected metabolite identification.
From: Large scale enzyme based xenobiotic identification for exposomics
a Time-dependent formation of 213.0981 m/z from caffeine. b Time-dependent formation of 216.1080 m/z from 13C3-caffeine. c Time-dependent formation of 216.1170 m/z from d3-caffeine. Annotated MS2 spectra of d 213.0981 m/z, e 216.1080 m/z, f 216.1170 m/z. Fragment interpretations are provided alongside labeled peaks. Proposed structures of unreported caffeine metabolite: g–i 213.0981 m/z, 216.1080 m/z, and 216.1170 m/z.
