Simulated moving bed (SMB) chromatography is a separation technique used in the pharmaceutical and fine chemicals industries, and in the field of bioengineering. It enables mixtures to be continuously separated and extracted in two fractions. Its efficiency is significantly higher than traditional batch chromatography, through better utilization of the column stationary phase.
But how does it work!
With normal chromatography the mobile phase (the eluent) flows down the static, stationary phase (the column bed). However, it has been recognised for many years that it would be more efficient if the stationary phase could also move, in a counter-current to the mobile phase. But having a moving column bed is not practical, so to get around this a “simulated” moving bed system was developed which simulates the conditions of a moving bed through a circulating flow of feed, extract, eluent, and raffinate (the raffinate being what is left after the extract has been removed).
The bulk of the eluent is continuously circulated in the system, making it necessary to replace only that small amount which is removed in the extract and raffinate. This enables savings of up to 90% of the eluent in comparison to a batch process. Also, due to the simulated counter-current, the stationary phase is significantly better utilized with the SMB technique as compared to the batch process technique. The number of theoretical plates might be also less important, making it possible to use cost-effective larger particle size for the stationary phases.
Typically, the SMB process is used for mixtures of two components, like chiral separations or mixtures with a “leading” or a “trailing” key product peak in the chromatogram. But it is possible that each partial fraction can be separated into a further fraction by repeated use of the SMB process – down to binary substance mixtures.
The KNAUER AZURA® SMB System Configuration
KNAUER has refined the SMB methodology further to produce a unique system that avoids the requirement for a large rotating multi-position valve, but instead utilizes seven smaller valves that gives the system greater efficiency and flexibility.
The AZURA® SMB systems consists of four pumps and seven multi-position valves. The devices are arranged as follows:
- Three pumps (Extract, Raffinate, Eluent) are placed inside the SMB cycle.
- The feed pump is placed outside the SMB cycle.
- Four valves are placed at the pump outlets.
- Three valves are placed at the pump inlets. The feed pump inlet is not connected to a multiposition valve.
Due to this configuration the SMB system can be used very flexible for many different separation modes. Additionally to the process stability AZURA® SMB systems are outperforming every other SMB system on the market regarding material and configuration flexibility as well usable pressure range.
KNAUER offers three versions of SMB systems; the AZURA® Lab-Scale SMB system in both stainless steel and biocompatible configurations, and the AZURA® Pilot-Scale SMB system. The lab systems are capable of producing kilograms of product per year and the pilot scale system up to 1000 kg of product per year.