Method for preparing sulfobutyl ether-β-cyclodextrin

A method for preparing sulfobutyl ether-β-cyclodextrin, the method consisting of specific preparation steps are as follows:

• Step (1):
• synthesis reaction:
• controlling the temperature at 20° C. to 30° C., adding an ether solvent and a sodium hydroxide aqueous solution having a concentration of 3.7 N into a reaction flask, increasing the temperature to 60° C. to 70° C., adding a β-cyclodextrin into the reaction flask;
• dropping an 1,4-sulfobutyrolactone to the reaction solution at 70° C. to 75° C., stirring the reaction solution at 70° C. to 75° C. after the dropping, controlling the reaction solution at pH>9 by adding a second sodium hydroxide aqueous solution having a concentration of 3.7 N, reducing the temperature to 20° C. to 25° C. when the percentage of unreacted β-cyclodextrin accounts for less than 0.5% wt of the total input of the β-cyclodextrin as measured by High Performance Liquid Chromatography, then adjusting the reaction solution to pH=7.0 to 7.5 with a concentrated hydrochloric acid, and providing an obtained mixed reaction solution in a purification operation in the next step directly;
• Step (2):
• purification:
• controlling the temperature at 20° C. to 30° C., adding the mixed reaction solution obtained in Step (1) into a dialysis bag, performing ultrasonic dialysis until the content of chloride ions is less than 10 ppm, decolorizing the dialysate by an absorbent active carbon, followed by filtrating to obtain a filtrate having ultraviolet absorption less than 0.5 AU, washing the active carbon twice by deionized water of 1 to 2 ml/g of the total input of the β-cyclodextrin, combining wash solution with the filtrate, concentrating the combined wash solution and filtrate by a 0.65 to 0.22 μm filter until the percentage of the sulfobutyl ether-β-cyclodextrin accounts for 30 wt % to 35 wt % of the total amount of the final solution, performing freeze-drying to obtain the sulfobutyl ether-β-cyclodextrin, and measuring an average 6.7 degree of substitution of the sulfobutyl ether group in capillary electrophoresis the amount of the ether solvent is 0.02 to 0.20 ml/g of the β-cyclodextrin.