How it works

The SMB process enables the separation of binary mixtures by means of a simulated countercurrent between the solid and liquid phases. This is accomplished with a series of chromatography columns arranged in a ring. An eluent flow circulates through this ring. Two inlets (for feed and eluent) and two outlets (extract/red and raffinate/blue) define four separation zones. By continuously feeding sample and synchronously switching the columns against the eluent flow direction, a countercurrent is achieved between the solid and liquid phases, leading to high purity of both target fractions.

The movement of the solid phase is realized by simultaneously switching seven multi-position valves (AZURA® SMB) or one central multi-position valve (former KNAUER SMB, CSEP®). 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, thereby enabling savings of up to 90% of the eluent in comparison to a batch process. Due to the simulated countercurrent, 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.