2.3. Purity by SEC-HPLC
Force-degradation and normal sample data were gathered by size-exclusive chromatography. We selected G3000SWXL (7.8 mm × 30 cm; TSK Laboratory, Tokyo, Japan), NaCl (Cat. No. 7647-14-5; Sigma-Aldrich, St. Louis, MO, USA), Na2HPO4 (Cat. No. 7558-79-4; Sigma-Aldrich), and NaH2PO4 (Cat. No. S5011-500G; Sigma-Aldrich). The sample was diluted to a concentration of 2 mg/mL by the addition of the preparation buffer and quantified at the absorbance of 280 nm in high-performance liquid chromatography. The column temperature was set at 25 ± 2°C. The column was pre-equilibrated with at least 10 column volumes of the mobile phase prior to sample injection (100 g each; 50 µL). The isometric elution time was 30 min.