Flip-flop chromatography

The flip-flop concept is an elegant way of dealing with feed mixtures consisting of components with very different adsorption behavior. However, it is not very often used due to the complexity of its operation and the system set-up. If the feed mixture contains components of very different elution behavior it is more advisable to use the above-mentioned concepts of precolumns or to divide the whole separation process into two steps a simple adsorption of the late-eluting impurities (see above) and the main separation. 

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A different concept dealing with highly adsorptive components is the so-called Flip-flop chromatography developed by Colin et al. (1991) (Fig. 5.8). The feed mixture is injected at the one end of the column and the early eluting components are pushed through the column (Fig. 5.8a) and collected at the other end (Fig. 5.8b). When the first components are withdrawn from the column the flow direction is reversed while the late-eluting component is still adsorbed on the column (Fig. 5.8c). After a predetermined time a new portion of feed mixture is injected and the elution is performed in the reversed flow direction (Fig. 5.8d). At the end of the column the late-eluting impurity from injection 1 is now eluted first (Fig. 5.8e) and afterwards the early-... 

Colin, H., Hilaireau, P., and Martin, M., Flip-flop elution concept in preparative liquid chromatography, /. Chromatogr., 557, 137, 1991. 

The use of the so-called flip-flop technique [13] in which the direction of flow in the column is reversed and the sample is injected alternately at either end of the column has been demonstrated to provide higher throughputs with reduced solvent consumption when used with elution chromatography. This approach requires the use of a column such as the Dynamic Axial Compression system manufactured by Prochrom, Champigneulles, France, where the stability of the packed bed is unaffected by the direction of flow. 

PS-SFC appears to be a complementary technique to preparative HPLC. Actually, it can be presented as one of the multiple alternatives to HPLC that aims at reducing the cost and solvent consumption while maintaining the efficiency of separation Simulated Moving Bed, Flip-Flop, Back-Flush, PS-SFC, Multi-Dimensional Chromatography, etc. On this basis, the potential applications of PS-SFC can be evaluat-... 

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