Continuous countercurrent chromatography

KeCler, L.C. and Seidel-Morgenstern, A. (2006) Theoretical study of multicomponent continuous countercurrent chromatography based on connected 4-zone units. 

Another approach to continuous reaction chromatography is the countercurrent moving-bed chromatographic reactor (CMCR). In this type of reactor the stationary (solid) phase travels in the opposite direction to the liquid phase. In practice this is performed by introducing the stationary phase from the top of the reactor. The stationary phase flows downwards under the influence of gravity while the liquid phase is pumped upwards from the bottom. A schematic presentation of such a system is shown in Fig. 7. Depending on the adsorption characteristics of the different components, they can travel in the direction of the liquid or the solid phase resulting in their separation. 

The countercurrent movement of a stationary phase is cumbersome in practice but it can be circumvented by an array of short columns connected by multi-position valves connected with eluent, feed, extract and raffinate, a method referred to as simulated moving bed chromatography (SMB) (Schulte and Strube, 2001). In SMB chromatography, the continuous countercurrent flow of the fluid and of the solid adsorbent is simulated by periodically switching the different inlets and outlets in the multi-column unit. Enantioselective SMB-LC has first been demonstrated for racemic 1-phenylethanol resolved on the polysaccharide CSP Chiralcel OD. In this pioneering work the principle of the method and the set-up has been depicted in a lucid educational fashion (cf. Figures 22 23) (Negawa and Shoji, 1992). 

Ito, Y., Foam countercurrent chromatography of bacitracin II. Continuous removal and concentration of hydrophobic components with nitrogen gas and distilled water free of surfactants or other additives,/ Chromatogr. 538 213 (1991). 

If the chromatographic process is designed with a continuous countercurrent flow of the fluid and the solid phase (Fig. 9.3), some of the disadvantages of elution chromatography, like product dilution and high solvent consumption, can be reduced. 

In a continuously operated production plant batchwise operation is a drawback. Principally speaking, the separation of a binary mixture with the components a and b can be carried out in a true moving bed (Seidel-Morgenstem et al. 2008). In Fig. 9.8-8 the principle of a countercurrent chromatography column is illustrated. The solid phase is moving downward whereas the mobile fluid phase is introduced at the bottom of the column. The feed of the components a and b is separated with the result that a raffinate containing a less adsorbable component a and an extract with the strong adsorbable component b are withdrawn as side streams. Therefore, the total column is subdivided into four zones ... 

Countercurrent Chromatography Procedure. The entire column (pair of coiled multilayer columns connected in series) was filled with the stationary phase. The apparatus was then rotated counterclockwise at 600 rpm in planetary motion while the mobile phase was pumped into the inlet of the column at a flow-rate of 2.2 mL/min (head to tail elution mode). Maximum pressure at the outlet of the pump measured 80 psi. After a 1-hour equilibration period, the sample was loaded into the Rheodyne injector loop and injected. Effluent from the outlet of the column was continuously monitored with a Shimadzu UVD-114 detector at 312 nm and fractions collected with a Gilson FC-lOO fraction collector to obtain approximately 8.8 mL of eluant in each tube (during a 4-min interval). Retention of the stationary phase was estimated to be 930 mL (74%) by measuring the volume of stationary phase eluted from the column before the effluent changed to mobile phase (330 mL) and subtracting this volume from the total column capacity of 1260 mL. 

Chen Fuming, Li Xuning, Wang Aiguo. The chromatography elution and fractional extraction method of spiral tube continuous countercurrent liquid-liquid extraction device china 200610063742.4[P]. 2006-12-31. 

Derosset AJ, NeuzdRW, Korous DJ Liquid column chromatography as a predictive tool for continuous countercurrent adsorptive separations, Ind Eng Chem Process Des Dev 15(2) 261-266, 1976. 

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