Dipotassium hydrogen phosphate anhydrous

Quercetin (purity ≥ 95%, Bangalore, Karnataka, India) and iron (III) chloride hexahydrate (purity ≥ 99%, Taufkirchen, Germany) were purchased from Sigma-Aldrich (Saint Louis, MO, USA). Dipotassium hydrogen phosphate anhydrous (purity ≥ 98%), potassium dihydrogen phosphate (purity ≥ 98%), sodium acetate anhydrous (purity ≥ 99%), hydrochloric acid (HCl, 37%), thiobarbituric acid (purity ≥ 98%), 1-butanol (purity ≥ 99.5%), and formic acid (FA, purity ≥ 98%) were purchased from PanReac AppliChem (Darmstadt, Germany). Furthermore, 2,4,4-tris(2-pyridyl)-1,3,5-triazine (TPTZ, purity ≥ 96%) was purchased from BLDpharm (Shanghai, China). Acetic acid (purity ≥ 99.8%) and ortho-phosphoric acid (purity ≥ 85%) were purchased from Component-Reaktiv (Moscow, Russia). Sodium thiosulfate standard titer was purchased from LLC Himtitry (Pereslavl-Zalessky, Russia). Starch indicator and sodium sulphate anhydrous were purchased from Himmed (Moscow, Russia). Acetic acid was purchased from Labtech (Moscow, Russia), and potassium iodide was purchased from Reahim (Moscow, Russia). Deionized water for chromatography (18 W) was obtained using a Milli-Q Merck water purification system (Millipore, Darmstadt, Germany).