Separation and Purification of 10-DAB III by Twin-Column Recycling Chromatography with a Step Solvent Gradient

10-Deacetylbaccatin III (10-DAB III) was isolated by twin-column recycling chromatography with the stationary phase of C18 silica gel and the eluent methanol/water (50/50, v/v). With introducing water as a modifier between the two columns, a spatial step solvent gradient was formed to reduce the eluotropic strength of the downstream liquid, which in turn generated a band compression to counteract band broadening, thereby improving the separation of 10-DAB III. After removing most of the easy-to-separate impurities, the columns could be dynamically switched based on the real-time change of the detection signal rather than be switched at a fixed interval. Thus, the separation process was robust and could accommodate the fluctuation of separating conditions. As a result, the purity and yield of the final 10-DAB III product reached over 99 and 90%, respectively. Also, investigations on operating conditions indicated that the separation efficiency could be enhanced by increasing the recycling number, solvent gradient, and feeding amount within the appropriate range.