Preparative Chromatography - Alternative Preparative Techniques > The Simulated Moving Bed Preparative Chromatography System > Page 59
A diagram of the cross-section of a valve including attached columns (the columns can be constructed of glass or metal depending on whether the system is to be used for GC or LC) is shown in figure 30. They are packed using standard packing procedures similar to those previously discussed. The design of the columns and column-disc connection allow easy column replacement if columns become damaged, contaminated or the stationary phase changed. The oblique shape of the columns allow the overall system to be relatively compact and, at the same time, have a reasonably high loading capacity.
Contemporary simulated moving bed systems that are used for preparative chromatography are mostly based on the Hurrel concept They all work basically on the same principle and the simple theory given for an actual moving bed devices will apply, albeit in a somewhat modified form. In modern simulated moving bed systems, the valving methodology has been developed further and is more complex. More recent systems are depicted somewhat differently as shown in figure 31 and can be oriented in a number of different ways, although they are all basically derivatives of the Hurrel system.
Figure 31. The Modern form of Depicting Simulated Moving Bed Technology