Chromatographic separation of praziquantel racemate using Simulated Moving Bed : from unit design to dynamic studies with online measurements

Abstract

This work studied a continuous chromatographic separation process known as Simulated Moving Bed (SMB) aiming the separation of the racemic mixture of praziquantel (PZQ). This racemate is primarily used to fight against schistosomiasis. The built-in-house SMB unit was validated and compared to that of the literature about concerning the praziquantel separation. Five of the eight performance parameters were superior to those in the literature, despite the feed-concentration of praziquantel being approximately ten times lower. Its dynamics was, approximately, ten times faster than those. Nonlinear absorption of ultraviolet-vis and circular dichroism signals were observed in the concentration measurement with the chiral detector equipment (JASCO model CD-2095), even in mixtures with low concentrations, however, the empirical model used showed a good fit. Based on an experimental open-loop study, with the chiral detector equipment coupled to the SMB unit, the following conclusions can be presented: (1) A step-change in the feed concentration revealed that the influence of the pumps, valves, and pipes located in between the columns had as a consequence a time lag to be accounted in future mathematical models, while their kinetic effects in the built-in-house SMB could be neglected and (2) A step-change in some volumetric flow rates revealed the importance to include in the mathematical model the fluctuations inherent to the experiments carried out.