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.