Purified starch (5 mg) was weighed, resuspended in water (0.9 mL), heated in a boiling water bath for 15 min under intermittent vortex mixing. The solution was then mixed with 0.1 mL of sodium acetate (0.1 M, pH 3.5), NaN3 (5 mL, 40 mg/mL), and 2.5 mL isoamylase, and heated in a water bath at 37 °C for 3 h. Afterward, 5 mL of anhydrous ethanol was added to the solution, followed by centrifugation at 4,000 rpm for 10 min. A DMSO/LiBr solution (1 mL) was added and dissolved by heating at 80 °C for 2 h.
The chromatographic device was a GPC-MALS system, consisting of a U3000 liquid-phase system (Thermo, USA), an Optilab T-rEX differential detector (Wyatt technology, CA, USA), and a DAWN HELEOS-II laser light scattering detector (Wyatt Technology, CA, USA).
According to the properties of specific compounds, gel exclusion columns (Ohpak SB-805 HQ: 300 × 8 mm, Ohpak SB-803 HQ: 300 × 8 mm) with appropriate molecular weight ranges were used, the column temperature was 60 °C, injection volume was 100 μL, mobile phase A was 0.5% LiBr and DMSO, the flow rate was 0.3 mL/min, and the gradient and isocratic elution for 120 min.
The chromatographic device was a GPC-MALS system, consisting of a U3000 liquid-phase system (Thermo, USA), an Optilab T-rEX differential detector (Wyatt technology, CA, USA), and a DAWN HELEOS-II laser light scattering detector (Wyatt Technology, CA, USA).
According to the properties of specific compounds, gel exclusion columns (Ohpak SB-805 HQ: 300 × 8 mm, Ohpak SB-803 HQ: 300 × 8 mm) with appropriate molecular weight ranges were used, the column temperature was 60 °C, injection volume was 100 μL, mobile phase A was 0.5% LiBr and DMSO, the flow rate was 0.3 mL/min, and the gradient and isocratic elution for 120 min.