Ultrahydrogel 120

For a detailed analysis of the soluble fraction of the hydrogel samples, it was isolated by continuous extraction in a Soxhlet apparatus with water for 24 h. After the process was completed solvent was evaporated and extracts were dried in an oven at 45 °C. For chromatographic analysis, extract solutions with concentration ca. 1 mg/mL were prepared. Molecular weight distributions were performed by means of gel permeation chromatography (GPC). The system of three columns Ultrahydrogel 2000 (Waters, Milford, MA, USA), Ultra Hydrogel 500 (Waters) and Ultrahydrogel 120 (Knauer, Germany) connected in series with the RI detector (Knauer, Berlin, Germany) was used. As an eluent 0.1 mol/L NaNO₃ solution in water was applied. The measurement was carried out at 25 °C, at a flow rate of 0.6 mL/min and sample volume of 100 μL was injected. A calibration using pullulan standards (Shodex, Yokohama, Japan) was performed.

For further investigation, the molecular weight distribution concerning the soluble fractions of the hydrogel was analysed. These were isolated by placing the hydrogel in distilled water for 24 h, after which the soluble fraction was decanted. This procedure was repeated three times. The water was then evaporated, and the extracts thoroughly dried at 45 °C. The dried aqueous extracts were subjected to GPC analysis. The concentration of the samples used for analysis was 5 mg/mL. GPC analysis was performed at 25 °C with an eluent flow rate of 0.6 mL/min. A three-column system consisting of an Ultrahydrogel 2000 (Waters, Milford, MA, USA), Ultrahydrogel 500 (Waters) and Ultrahydrogel 120 (Knauer, Germany) was connected to an RI detector (Knauer, Berlin, Germany). A 0.1 mol/L aqueous solution of NaNO₃ with the addition of sodium azide was used as the eluent. Pullulan standards (Shodex, Yokohama, Japan) were used to calibrate the instrument.