Chromatographic processes elution chromatography

Presently, there is considerable interest in the preparative applications of liquid chromatography, even though it is often considered expensive. To make the chromatographic process more attractive, attention is focused on the choice of the operating mode in an effort to minimize eluent consumption and to maximize productivity, which is of key importance when expensive packings are used. Among the alternatives to the classical process (elution chromatography), much attention is paid to SMB. 

Development of the Chromatogram. The term development describes the process of performing a chromatographic separation. There are several ways in which separation may be made to occur, eg, frontal, displacement, and elution chromatography. Frontal chromatography uses a large quantity of sample and is usually unsuited to analytical procedures. In displacement and elution chromatography, much smaller amounts of material are used. 

At present, the purification by chromatographic processes is the most powerful high-resolution bioseparation technique for many different products from the laboratory to the industrial scale. In this context, continuous simulated moving bed (SMB) systems are of increasing interest for the purification of pharmaceuticals or specialty chemicals (racemic mixtures, proteins, organic acids, etc.).This is particularly due to the typical advantages of SMB-systems, such as reduction of solvent consumption, increase in productivity and purity obtained as well as in investment costs in comparison to conventional batch elution chromatography [1]. 

The three main modes of chromatographic operation are elution chromatography, selective adsorption/desorption, and simulated countercurrent chromatography. Of these, elution chromatography, used as a cyclic batch process, was the first to be developed for large-scale separations. 

Many different products are now purified by chromatographic processes, from the laboratory scale (a few grams) up to the industrial pharmaceutical scale (a few tons per year) or even up to the petrochemical scale (100,000 tons per year). Among the possible technologies, the elution high-performance liquid chromatography (HPLC) technology (sometimes with recycle) has taken a very important part of the small-scale (10 tons per year) market... 

An example of virus clearance factors in chromatographic processes frequently used for purification of antibodies is given in Table 17. Lower clearance factors for protein A affinity chromatography have been found by Mariani and Tarditi128 when compared to results found with protein G by Walter and Allgaier.237 An explanation of this fact can be found in the fact that protein G requires harsher elution conditions than protein A. 

The development of preparative chromatographic processes in fine chemistry and in pharmaceutical industries is a very important field of research. This new process called SF-SMB (Supercritical Fluid Simulated Moving Bed) is a attempt to optimize preparative chromatography by three ways the choice of a supercritical C02 as eluent, the implementation of the simulated moving bed, and the use of an elution strength modulation in the process, performing a pressure gradient. 

In chromatography, a series of signals from the detector output is registered as the chromatogram. The qualitative information is derived from the retention time, tms, which is determined by the chromatographic process and which depends on the thermodynamic properties of both the stationary phase and the solutes. The quantitative information stems from the area under the signal, and is determined by the measurement process and depends on the detector properties. In so doing, it is assumed that the sample component elutes quantitatively from the analytical column. 

Thus, it will be extremely difficult at best to separate the influences of the various phenomena that may be responsible for the effects of a slow kinetics of mass transfer and a slow kinetics of the retention mechanism. The fitting of experimental data obtained in overloaded elution chromatography to various models of chromatography will not permit the choice of a best model, nor the identification of the slowest step in the chromatographic process. Independent measurements of the kinetic parameters are necessary. 

Vacancy Chromatography A chromatographic process in which a sample solution is used as the mobile phase and a sample of pure solvent is injected periodically. A vacancy of each component migrates along the column, instead of a positive peak in conventional elution. 

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