Determination of the Molecular Mass of Modified Citrus Pectin Using High-Performance Size Exclusion Chromatography

Modified citrus pectin (MCP) is a polysaccharide with antitumor growth activity, anti-invasiveness activity, and anti-metastasis activity. Its pharmacological activities are greatly influenced by its molecular mass and polydispersity; therefore, it is necessary to determine the molecular mass and polydispersity of MCP. At present, there has been no report on the determination of the molecular mass of MCP using high-performance size exclusion chromatography-refractive index detection (HPSEC-RID). In this study, a TSK G3000PWXL column was used at 40°C with the mobile phase of 50 mmol/L NH4Ac at the flow rate of 0.5 mL/min. The injection volume of MCP was 20 μL, with the mass concentration of 10 g/L. Pullulan standards with known molecular mass were chosen as the calibration standards to obtain the regression equation. The relative molecular mass of MCP was derived from the regression equation: Mn was 21000; Mw was 43000; Mp was 46000; and Mz was 66000. The polydispersity index of MCP was 2. This method is simple, rapid, and reproducible for quality control in MCP production, and it would be also applicable to the study of composition-activity relationship of MCP in the future.