基膜为80000的聚砜超滤膜经原位生成法制备得磁性超滤膜。在压力为0．2MPa条件下改变磁场强度，其截留相对分子质量可调控范围为31000-73000。利用此膜对纯度为97．5％的当归多糖进行连续分级分离，在不同磁场强度下得到3个样品（A、B和C）。高效凝胶色谱法测定样品A、B以及C的重均相对分子质量分别为86317、19989、62461，样品A中相对分子质量为70000-100000的当归多糖占70％左右；样品B中相对分子质量为10000-30000的当归多糖占95％左右；样品C中相对分子质量为500%A magnetic ultrafiltration membrane whose molecular weight cut-off （MWCO） can be between 31000 and 73000 under 0.2 MPa pressure and varying magnetic field intensity was prepared by in situ synthesis on the basis of a polysulfone ultrafiltration membrane with a MWCO of 80000 and used sequentially separate Angelica sinensis root polysaccharides with a purity of 97.5%. As a result, three fractions were obtained under various magnetic filed intensities and named as A, B and C, respectively. Their respective weight average molecular weights （M,） were determined by high performance gel permeation chromatography （HPGPC） to be 86317, 19989 and 62461. Polysaccharides with a relative molecular weight ranging from 70000 to 100000 was 70% in fraction A. Roughly 95% of fraction B consisted of polysaccharides with a relative molecular weight between 10000 and 30000. Fraction C contained approximately 80% of polysaccharides whose molecular weight was in the range of 50000 - 70000.
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