Hagen Kniep

Comparison of Various Process Engineering Concepts of Preparative Chromatography

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. 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. 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 to enhance yields and productivities. In spite of a number of attempted comparative studies, 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.

Separation of Enantiomers through Simulated Moving-Bed Chromatography

The application of SMB (simulated moving-bed) chromatography for the resolution of two racemic mixtures shall be described. First, a simple mathematical model of the chromatographic process as well as the methods for the determination of the essential parameters are defined, then the results of various SMB experiments are presented and compared to model predictions.

Optimization of solvent gradients for chromatographic separations

In this paper preparative gradient chromatography is mathematically described using a simple cell model. The model enables the simulation of single elution profiles as well as the systematic optimization of the operating parameters. Experimental investigations were carried out for the model system benzyl alcohol/2-phenyl ethanol/toluene separated on a RP18 stationary phase with mixtures of water and acetonitrile as eluant. In the experiments different linear changes in the eluant strength were applied.