Liquid chromatography utilising porous solid phases (adsorption chromatography) is one of the most powerful and versatile methods of modern analytical chemistry. Its widespread application is due in part to the development of a broad range of combinations of solid stationary and liquid mobile phase. Normal phase and reverse phase chromatography with pure and chemically modified silica gel, respectively, affinity chromatography, and ion chromatography can be cited as examples [1]. In addition to its use as an analytical method, chromatography is becoming increasingly important in the preparative‐scale isolation of pure substances in the pharmaceutical industry, in biotechnology, and in the production of fine chemicals. In many cases, the required purity criteria can only be met with chromatographic techniques, as in the resolution of racemates. From a process engineering viewpoint, a better understanding of concentration profile deformations caused by intended overloading of separation columns has recently been acquired [2]. In particular, this cncerns the description of displacement and entrainment effects associated with the competing adsorption. A series of alternative operating modes has been developed and used [3] for enhancing yields and productivities. In spite of a number of attempted comparative studies [4] there is a lack of quantitative information about optimized process. This article aims to compare four different process engineering concepts of preparative chromatography on the basis of a uniform theoretical model.

Liquid chromatography utilizing porous solid phases (adsorption chromatography) is one of the most powerful and versatile methods of modern analytical chemistry. Its widespread application is due in part to the development of a broad range of combinations of solid stationary and liquid mobile phases. Normal phase and reverse phase chromatography with pure and chemically modified silica, respectively, affinity chromatography, can be cited as examples [1]. In addition to its use as an analytical method, chromatography is becoming increasingly important in the preparative scale for the isolation of pure substances in the pharmaceutical industry, in biotechnology, and in the production of fine chemicals. In many cases, the required purity criteria can only be met with chromatographic techniques, as in the resolution of racemates. From a process engineering viewpoint, a better understanding of concentration profile deformations caused by intended overloading of separation columns has recently been acquired [2]. In particular, this concerns the description of displacement and entrainment effects associated with the competitive adsorption. A series of alternative operating modes has been developed and used [3] to enhance yields and productivities. In spite of a number of attempted comparative studies [4], quantitative information about optimizing these processes is lacking. This article will compare four different process engineering concepts of preparative chromatography on the basis of a uniform theoretical model.

Due to increasing purity requirements, temperature sensitivity and complexity of feed mixtures, chromatographic separations are more and more applied to purify value added products. Frequently, gradient chromatography is used to reduce the duration of batch separations of mixtures with very different retention times of the components. In this case the retention times of the slowly migrating components are reduced by increasing the elution strength of the eluant.

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