Waters 2414 differential refractive index detector

The precolumn derivatization approach was used to determine the monosaccharide composition of polysaccharides [17 (link)]. The sample was dissolved by adding 3 mg of polysaccharide to 1 mL of distilled water and hydrolyzed with 1 mL (4 mol/L) of trifluoroacetic acid (TFA) at 110 °C for 6 h. The residual TFA was then removed by adding methanol. 1 mL of hydrolysis product was added to distilled water for derivatization. After derivatization, the derivatives filtered through a 0.22-μm membrane were detected by an Agilent Eclipse XBD-C18.
The relative Mw of polysaccharides was measured using a high-performance liquid chromatography system equipped with a Waters-2414 differential refractive index detector (Waters Co., Milford, MA, USA). A G4000SWXL column (7.8 × 300 mm, Tosoh Co., Ltd. Tokyo, Japan) was used. The column temperature was 40 °C, and 0.1 M sodium nitrate solution was used as the eluent. The relative Mw of polysaccharides was calculated according to calibration curves (Log Mol Wt = 1.27e − 8.10e⁻¹ T, R² = 0.9943) of the dextran standards (Sigma Co., St Louis, MI, USA), including 667,000 Da, 413,000 Da, 76,900 Da, 43,500 Da, 10,500 Da, and 5000 Da.

The molar masses (M_w), molar mass distributions, and polydispersity index (M_w/M_n) of the synthesized P(DMAEMA-co-OEGMA) copolymers were determined by SEC, using a Waters instrument (Waters Corporation, Milford, MA, USA). The chromatography system consists of a Waters 1515 isocratic pump (Waters Corporatione, Milford, MA, USA), a set of three m-Styragel mixed pore separation columns (pore size 10²–10⁶ Å), and a Waters 2414 differential refractive index detector (equilibrated at 40 °C) (Waters Corporation, Milford, MA, USA). The measurements and data analysis were performed using the Breeze software (version 3.2) (Waters Corporation, Milford, MA, USA). Tetrahydrofuran containing 5% v/v trimethylamine was the mobile phase, at a flow rate of 1 mL/min, and the temperature was set at 30 °C. Linear polystyrene standards with average molecular mass in the range of 1200–929,000 g·mol⁻¹ and narrow molecular mass distributions were utilized for setting up the calibration curve. P(DMAEMA-co-OEGMA) copolymers were soluble in the mobile phase and were measured at concentrations in the range of 2–4 mg mL⁻¹.