Chromatographic processes displacement chromatography

The development of displacement separations has historically been an empirical process and even though chromatographic theory may guide the selection of operating conditions the final stage must involve experimental validation. Typically, several experiments will be carried out at or near the conditions determined by the theory. The final stage in the procedure is either experimental or numerical optimization of the displacement process to produce optimal yields, purities and productivities. At this point, the relative efficacy of selective and conventional displacement chromatography can also be evaluated. 

Displacement chromatography A chromatographic process in which, after the sample is injected, the mobile phase is replaced by a solution of a compoxmd more strongly adsorbed than any feed component, the displacer. Eventually, the feed components are separated into a series of successive zones, forming an isotachic train which propagates without further change. If the column efficiency, the sepa-... 

Gas bulk-seperalion processes consist mostly of PSA variations and displacement-purge and inert-purge procesrea These cycles are discussed below. Also, even (hough chromatography is covered in another chapter, reference is made hare and in following sections 10 several commercial chromatographic processes fur completeness of the discussion,... 

Also, the mechanism of separation based on displacement chromatography followed by enrichment in a CCC column was studied, and a tenfold enrichment of the transition metal ions was observed in the stationary phase. However, diffusion of the sample is an inherent process in chromatographic elution spreading of the sample bands in the column is unavoidable in CCC as it is in conventional LC. 

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. 

Isolation procedures for many biochemicals are based on chromatography. Practically any substance can be selected from a crude mixture and eluted at relatively high purity from a chromatographic column with the right combination of adsorbent, conditions, and eluant. For bench scale or for a small pilot plant, such chromatography has rendered alternate procedures such as electrophoresis nearly obsolete. Unfortunately, as size increases, dispersion in the column ruins resolution. To produce small amounts or up to tens of kilograms per year, chromatography is an excellent choice. When the scale-up problem is solved, these procedures should displace some of the conventional steps in the chemical process industries. 

A chromatographic separation can be developed in three ways, by displacement development, by frontal analysis, and by elution development, the last being almost universally used in all analytical chromatography. Nevertheless, for the sake of completeness, and because in preparative chromatography (under certain conditions of mass overload) displacement effects occur to varying extents, all three development processes will be described. 

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