Oxidized bases were well separated with 5-OHC at a retention time of 23.5 min, FapyA at a retention time of 29.3 min, 8-OHA at a retention time of 34.6 min, FapyG at a retention time of 42.2 min, and 8-OHG at a retention time of 47.2 min. Figures 2B-E show representative mass spectra of stable isotope labeled 8-OHG (m/z 443 and 458) (B), stable isotope labeled 8-OHA (m/z 355 and 370) (C), stable isotope labeled FapyG (m/z 445 and 460) (D),stable isotope labeled FapyA (m/z 357 and 372) (E), and stable isotope labeled 5-OHC (m/z 331 and 346) (F).
