Preparative chromatography continuous

There are many advantages of the SMB technology compared to batch preparative chromatography. The process is continuous and the solvent requirement is minimal compared to batch. In SMB, the whole stationary phase is used for the separation while in batch chromatography only a small part of the column is involved in the separation. This allows optimization of productivity with respect to the stationary phase. 

Keywords Preparative chromatography, Simulated moving bed chromatography, Continuous separation technique, Triangle theory, Bioseparation... 

In preparative chromatography, the information provided by the isotherms and by the proper model of chromatography will help the scale-up and optimization of batch and continuous purifications with minimum use of solvents and sample. Although it is rather difficult to give straightforward instructions how to optimize a preparative separation, some general guidelines are provided in this chapter. 

When compared to the batchwise preparative chromatography, Simulated moving bed (SMB) units exhibit a number of advantages. These advantages are primarily because of the continuous nature of the operation and the efficient use of the stationary and mobile phases, which allows a decrease in desorbent requirement and an improvement of the productivity per unit time and per unit mass of stationary phase. In addition, high performances can be achieved even at rather low values of selectivity and with a relatively small number of theoretical plates. Due to these positive features, SMB is particularly attractive in the case of enantiomer separations, since it is difTicult to separate enantiomers by conventional techniques. More recent applications related to chiral technology were reported [1-3]. 

Preparative chromatography is a proven technology for the separation of specialty chemicals mainly in food and pharmaceutical industries, particularly the enantioseparation of chiral compounds on chiral stationary phases. The potential of preparative chromatographic systems were further increased by the development of continuous chromatographic processes like the simulated moving bed (SMB) process. Compared to the batch column chromatography, the SMB process offers better performance in terms of productivity and solvent consumption [2]. 

The possibility of zonal sample dosage in equilibrium conditions (after the front of mobile-phase and continuous-chromatogram development, which is provided by a horizontal sandwich chamber) was utilized by Glowniak et al. [3] in preparative chromatography of simple coumarins and furano-coumarins found in Archangelica fruits, performed with a short-bed continuous development (SB-CD) technique. 

Automation allows batch chromatography to be run as a continuous process. Multiple injections using a separate pump and fraction collection provide an opportunity for continuous unattended operation. In iso-cratic separations, sample injection is often made before previously injected product elutes from the column, thus reducing cycle time and solvent consumption. Continuous and automated processes are always used with smaller columns and lower amounts of expensive enantioselective stationary phases. One of the future goals for modern PHPLC optimization would be the creation of software that would allow computer simulation modeling of nonlinear effects in preparative chromatography. 

Carr, R. W. Continuous reaction chromatography, in Preparative and Production Scale Chromatography, Ganetsos, G., Barker, P. E. (Eds.), Marcel Dekker Inc., New York, 1993. 

Preparative chromatography will continue to play a role of major importance as a separation process in the pharmaceutical and biotechnological industries in the next quarter of a century. A number of different processes are already used. Some of them will imdergo considerable improvement. A few others will be invented or developed. There is presently no simple way to have easy access to the... 

Rotating annular column An implementation of preparative chromatography using a cylindrical, annular column rotating aroimd its axis. A continuous feed stream is injected at a fixed position just above the packing. Each component band follows a helical trajectory and is collected as a continuous stream along a fixed sector of the outlet annulus. 

Simulated Moving Bed An implementation of preparative chromatography in which a series of identical columns is used. The continuous injection of a feed stream and of the mobile phase stream, the continuous collection of two fraction streams are made in positions which are periodically moved by one column length. The result is a semisteady concentration profile for each component, which oscillate slowly, and permits the collection of two streams of constant composition. The process is equivalent to moving the stationary phase down the column while the mobile phase flows upward, the faster moving component eluting at the top, with the mobile phase, the slower moving one at the bottom, writh the stationary phase. 

Many industrial or preparative separation processes are elution processes. In elution processes a pulse of sample followed by eluent is continuously fed, and another stream is continuously recovered. However, product leaves the system in pulses, making this process a batch process. This is different from a continuous process, in which feed and product streams are continuously fed and recovered, respectively, and are at steady state. Semi-continuous processes alternate between continuous product and regeneration cycles. Simple fixed bed adsorption is an example of a semi-continuous process, while distillation is an example of a continuous process. Chromatography is typically an elution process although continuous forms of this separation have been reported (1-4). 

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