8 isoprostane d4

8-isoprostane (8-iso prostaglandin F2α, 8-epi PGF_2α) and 8-isoprostane-d⁴ were purchased from Cayman Chemicals (Ann Arbor, MI, USA). Acetic acid (AA) was purchased from Sigma-Aldrich (St. Louis, MO, USA) and formic acid was purchased from J. T. Baker (Phillipsburg, NJ, USA). Optima LC-MS grade water, acetonitrile, methanol, and other chemicals were purchased from Fisher Scientific (Fairlawn, NJ, USA).

8-OHdG (≥98%) (2-amino-9-[(2R,4S,5R)-4-hydroxy-5-(hydroxymethyl)oxolan-2-yl]-1,7-dihydropurine-6,8-dione) in a solid form was obtained from Merck (Buchs, St. Gallen, Switzerland). [¹⁵N5]-8-OHdG as internal standard (IS) was obtained from Cambridge Isotope Laboratories (Tewksbury, MA, USA). 8-Isoprostane ((5Z,8β,9α,11α,13E,15S)-9,11,15-trihydroxyprosta-5,13-dien-1-oic acid) in a solution ≥ 95%, and its deuterated IS 8-Isoprostane-d₄ ((5Z,8β,9α,11α,13E,15S)-9,11,15-trihydroxyprosta-5,13-dien-1-oic-3,3,4,4-d4 acid), were obtained from Cayman Chemical (Ann Arbor, MI, USA). HPLC grade methanol (≥99.9%) was obtained from Merck (Buchs, Switzerland). LC-MS grade solvents; methanol (≥99.95%) and acetonitrile (≥99.9%) were obtained from Carlo Erba Reagents (Chaussée du Vexin, Val de Reuil, France). Butylated hydroxytoluene (BHT) ≥ 99% was obtained from Sigma-Aldrich Produktions GmbH (Steinheim Germany). LC–MS grade acetic acid was obtained from Honeywell (Seelze, Germany). Ultrapure water was produced in our laboratory with a Milli-Q Advantage water purification system (18.2 MΩ.cm at 25 °C, <3 ppb total organic carbon).

Both 8-hydroxy-2′–deoxyguanosine (purity ≥ 98%) and 5-hydroxymethyluracil (purity 97%) were purchased from Sigma-Aldrich (St. Louis, MO, USA), and 8-hydroxy-2′-deoxyguanosine-15N5 (purity 95%) was purchased from Cambridge Isotope Laboratories, Inc. (Tewksbury, MA, USA). 8-hydroxyguanosine (purity ≥ 98%), 8-isoprostane (purity ≥ 99%), and 8-isoprostane-d4 (purity ≥ 99%) were obtained from Cayman Chemical (Ann Arbor, MI, USA). 8-hydroxyguanosine-13C,15N2 (purity 98%), 4-hydroxynonenal (purity ≥ 98%), and 4-hydroxynonenal-d3 (purity 97%) were purchased from Santa Cruz Biotechnology (Dallas, TX, USA). Methanol (LC-MS grade) was purchased from Burdick and Jackson (Muskegon, MI, USA). Formic acid and ammonium hydroxide were obtained from Sigma-Aldrich (St. Louis, MO, USA). Strata-X-A cartridges (33 µm Polymeric Strong Anion, 200 mg/3 mL; 8B-S123-FBJ), analytical columns (Kinetex phenyl-hexyl column, 100 mm × 4.6 mm, 2.6 µm particle size; 00D-4495-E0), and Kinetex C18 column, (100 mm × 4.6 mm, 2.6 μm particle size, 00D-4462-E0) were purchased from Phenomenex (Torrance, CA, USA).