1260 infinity gpc sec system

Molecular weights and molecular weight distributions were determined using an Agilent 1260 Infinity GPC/SEC system. The GPC system was equipped with a refractive index (RI) detector. The molecular weights were estimated relative to near-monodisperse poly(methyl methacrylate) standards (2.14 × 10⁶–1.95 × 10³ g mol⁻¹ range). DMF with 0.1% LiBr was used as the mobile phase at a flow rate of 1.0 mL min⁻¹. Samples were prepared at a 1 mg mL⁻¹ concentration using a solution of DMF, 0.1% LiBr, and 0.1% toluene as a marker reference. Samples were filtered through a 0.45 mm PTFE syringe before injection.

The molecular weight of the extracted pectin was assessed by size-exclusion chromatography (SEC; 1260 Infinity GPC/SEC System, Agilent), equipped with a PL aquagel-OH MIXED-H 8 μm column. The samples were dissolved overnight at 2 mg/mL concentration in a recommended buffer (0.2 M NaNO₃ + 0.01 M NaH₂PO₄ at pH 7), and, then, filtered through a 0.45 μm membrane (Titan 3, PTFE, ThermoScientific, UK) prior to injection (20 μl). The column set was calibrated with narrow pullulan standards and, thus, all molecular weight values were determined.

The number average molecular weight (M_n), the weight average molecular weight (M_w) and the polydispersity index (Đ) of NR, CR, BR and each functionalised rubber were determined by performing gel permeation chromatography (GPC) using Agilent Technologies 1260 Infinity GPC/SEC system equipped with a refractive index (RI) detector and PLgel 5 μm MIXED-C columns (300 × 7.5 mm, M_w range of 200 to 2 000 000 g mol⁻¹). Calibration was carried out using polystyrene standards (M_w range from 162 g mol⁻¹ to 6 570 000 g mol⁻¹) from Agilent Technologies, Inc. Samples were prepared at least 48 hours prior to the analysis by dissolving approximately 10 mg of sample in 5 mL of THF. The solutions were then filtered through a 0.2 μm PTFE syringe filter and transferred into GPC vials. Each run was performed by injecting 100 μL in the columns, kept at a constant temperature of 25 °C, with a flow rate of fresh THF of 1 mL min⁻¹ for 40 min.