During Optimization of Chromatographic Systems

Name (nature) Manufacturer Type Fract range (kDa) pH-stability Organic solvent stab. 

In preparative chromatography the systems are mainly operated at high feed solubilities and thus thermodynamic effects dominate. If separations with low feed solubilities have to be operated, high-efflciency adsorbents should be used and the ACD injection technique could be applied (Section 3.2.3.2). 

Thermodynamic effects are the main source of increasing productivity in preparative chromatography. The most important parameter is the selectivity, which describes the ratio of the initial slopes H of the adsorption isotherms for both components (Equation 2.46). 

Especially for feed mixtures with different ratios of the single components, the elution order must be considered. The major component should elute as the second peak, because in this case the displacement effect can be used to ease the separation (Section 2.6.2). If the minor component elutes as the second peak the tag-along effect reduces the purity and loadability of the system. 

If the components to be separated are present in a similar amount (e.g., as for racemic or diastereomeric mixtures) the target component should elute first, because the first peak is normally obtained at higher productivity and concentration. 

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