Method for purifying and preparing sulfobutyl ether-Beta-cyclodextrin through membrane separation and solvent precipitation

The invention provides a method for purifying and preparing sulfobutyl ether-Beta-cyclodextrin through membrane separation and solvent precipitation. The method comprises the steps: removing impurities such as micromolecular unconverted reactants and salt passing through an ultrafiltration membrane which has a certain aperture, wherein the product sulfobutyl ether-Beta-cyclodextrin is retained and concentrated; then separating the sulfobutyl ether-Beta-cyclodextrin from the mother liquor by using a solvent precipitation method based on the characteristic of the sulfobutyl ether-Beta-cyclodextrin that the sulfobutyl ether-Beta-cyclodextrin is insoluble in absolute ethyl alcohol; and finally processing the sulfobutyl ether-Beta-cyclodextrin by vacuum drying so as to obtain a solid product. And the mother liquor can be distilled to recover the ethanol for recycling. The method is novel in conception, has simplicity in technology, low investment on equipment, energy conservation and consumption reduction in produ