SEC-MALLS法测定普鲁兰糖相对分子质量及分子质量分布

目的: 建立分子排阻色谱-多角度激光散射(size exclusion chromatography-multiangle laser light scattering,SEC-MALLS)系统测定普鲁兰糖的相对分子质量及分子质量分布的方法. 方法: 采用2根Shodex SB-806HQ色谱柱(300 mm×7.8 mm,10 μm)串联,以水为流动相,流速0.5 mL · min^-1,柱温35 ℃,检测器为多角度激光散射器(MALLS)和示差折光检测器(refractive intex detector,RID)联用,对普鲁兰糖的相对分子质量及分子质量分布进行测定,并对均方根旋转半径(r_g)与样品在溶液中的聚集态进行分析;同时还以传统凝胶渗透色谱(GPC)法对普鲁兰糖的相对分子质量及分子质量分布进行测定,并对2种方法测定的结果进行分析比较. 结果: SEC-MALLS法测定普鲁兰糖样品的结果与GPC法测定的结果比较,2种系统测定的重均相对分子质量及分子质量分布结果基本一致,同时测得普鲁兰糖在水溶液中为无规线团构象的线性聚合物. 结论: SEC-MALLS法测定相对分子质量无需分子量标样,可以同时获得样品在溶液中的聚集态和构象信息,可用于普鲁兰糖的质量控制.

Objective: To establish a method for determination of relative molecular mass and molecular mass distribution of pullulan with SEC-MALLS. Methods: The process was performed on two tandem Shodex SB-806HQ columns (300 mm×7.8 mm,10 μm) at 35 ℃.The flow rate of mobile phase composed of water was 0.5 mL · min^-1.The relative molecular mass and molecular mass distribution were determined by on-line multi-angle laser light scattering detector connected with refractive index detector(RID).By plotting the RMS radius versus the molar mass for pullulan,the aggregation and conformation were investigated.These results were compared with conventional GPC measurements. Results: The weight-average relative molecular masses and molecular mass distribution determined by SEC-MALLS closely agree with the ones derived from using GPC by establishing calibration curve.Meanwhile,the aggregation and conformation were determined by SEC-MALLS. Conclusion: This method of SEC-MALLS can not only provide absolute values of the molecular weight,but also yield information on conformation of the RMS radius and branching characteristics independent of the chromatographic conditions or the elution volumes.Therefore,the combination of SEC and MALLS can be applied for the determination of relative molecular mass and molecular mass distribution of pullulan and other polymers.