Ultrahydrogel tm 500 column

The Mw and polydispersity index (PI) of pectin samples were determined by a high performance size exclusion chromatography (HPSEC) system according to the method described by Guo with some modifications^{46 (link)}. The average Mw determination was performed on a Waters 1525 HPLC system (Waters, Milford, USA) with ultrahydrogel TM 500 Column (Waters, Milford, USA). Forty microliters of the pectin solutions (2.0 mg/mL) were injected and eluted by 0.2 M NaCl at a flow rate of 0.5 mL/min. The standard dextrans of 1.27, 11.60, 5.22, 48.60, 147.60, 273.00, 409.80 and 667.80 kDa were used to obtain the calibration curves. The average Mw and PI of pectin samples and standard dextrans was calculated using the Breeze 2 software.

The MW distribution was analyzed by high-performance gel permeation chromatography (HPGPC) as reported previously [14 (link)]. A Waters HPGPC instrument was used consisting of a Waters 1515 isocratic HPLC pump, a Waters 2414 refractive index (RI) detector, and a Waters 2998 UV detector. Two columns were used in series, the Ultrahydrogel TM 2000 and Ultrahydrogel TM 500 column (Waters). Water was used as the mobile phase. The MW calibration was performed with several dextran MW standards ranging from 1.0 to 670 kDa (Sigma-Aldrich, St. Louis, MO, USA). The sample and standards were dissolved in DI water and filtered through a 0.22 μm membrane before being injected into the instrument system.