2.1. Chemicals and reagents

Standard stock solutions (10 or 100 ppm) of individual isoprostane and their respective deuterated internal standards were purchased at the highest available purity from Cayman Chemical Company (Ann Harbor, Michigan). Target isoprostanes include 8-iso-prostaglandin F2α (8-iso-PGF2α), 2,3-dinor-8-iso-prostaglandin F2α (2,3-dinor-iPF2α-III); a major metabolite of 8-iso-PGF2α), prostaglandin E₂ (PGE2), and 5-iPF2α-VI and the corresponding internal standards include 8-iso-PGF2α-D₄, PGE2-D₄, and 5-iPF2α-VI-D₁₁. HPLC grade methanol and formic acid were purchased from Fisher Scientific (Hampton, NH). β-glucuronidase type H-2 enzyme (≥85,000 units/mL; extracted from Helix pomatia) was purchased from Sigma Aldrich (St. Louis, MO). Ultrapure water was prepared using a Thermo Fisher Scientific MicroPure UV system. All standard solutions of target isoprostanes were stored at −20 °C.