>99%),
sodium
acetate (purity ≥99%), K2HPO4·3H2O (purity ≥99%), acetic acid (purity ≥99.5%),
2,4-dinitrofluorobenzene (purity ≥98%), and NaHCO3 (purity ≥99.8%) were all provided by Shanghai Macklin Biochemical
Co., Ltd. NaOH (purity >96%) was obtained from Tianjin Jinbei Fine
Chemical Co., Ltd. HCl (36%–38%, w/w) was purchased from China
Pingmei Shenma Group Kaifeng Dongda Chemical Co., Ltd. Acetonitrile
(chromatographic grade) was provided by Tianjin Kemiou Chemical Reagent
Co., Ltd.