Ascorbate concentrations in cell lysates, tissues, and plasma were measured using reverse-phase high-performance liquid chromatography (HPLC; Waters 600 HPLC; Waters, MA, USA) with an ESA Coulochem II detector (Thermo Fisher Scientific), as described before.19 (link),22 (link),23 (link) A fresh standard curve of 0–40 μM ascorbate was prepared for each HPLC run.