(292b) Determination of the Competitive Isotherms of Enantiomers by a Hybrid Inverse Method Using Overload Band Profiles and the Periodic State of the Smb Process

In the present work a numerical method was developed and tested to determine adsorption isotherms in simulated moving bed (SMB) chromatography. The numerical parameters of prescribed adsorption isotherm model are derived using a hybrid inverse method, that incorporates overload band profiles of the racemic mixture, which includes breakthrough data from a single frontal analysis to overcame the shortcoming arising from the underestimation of the saturation capacity, once the concentration range sampled by the bands is diluted with regards to concentration injected; and the cyclic steady state (CSS) concentration profile of an SMB experiment. Each competitive adsorption isotherm model is coupled with an axially dispersed flow model with finite mass transfer rate to describe the experimental band profiles. The numerical constants of the isotherms models are tuned so that the calculated and measured band profiles match as much as possible.

This method was applied to determine the binary adsorption isotherms of the two enantiomers of Trögers base on a system made of pure methanol as the mobile phase and of Chiralpak AD. We show that this numerical inverse method can be applied even without the knowledge of the individual band profile of the pure solutes. The results indicate that the hybrid inverse method offers a reliable and quick approach to determine the competitive adsorption isotherms for a specific SMB separation.

Keywords: competitive isotherms; chiral separations; inverse method; band profiles; cyclic steady state; simulated moving bed chromatography.