Distinguish Overload chromatography (see outline). 

See also purification of antibodies using CEX displacement mode chromatography and overload chromatography 

See also purification of antibodies using AEX displacement mode chromatography and overload chromatography

Displacement chromatogrphy employs a displacer compound to remove components of a mixture from a column. The displacer compound generally has a much higher affinity for the stationary pahse than do any of the components in the mixture to be seaprated. This is in contrast to elution chromatography, where the eluent has a lower affinity for the stationary phase than do the components to be separated. A key operational feature that distinguishes displacement chromatography from elution or desorption chromatography is the use of a displacer compound. (Little, US2007/0102363). 

Displacement mode (displacement chromatography): means operating a known chromatography column/assembly in a displacement mode (using a displacer molecule) instead of operating it in the elution mode (using an elution buffer/buffer solution). It is a method of eluting species bound to a chromatography column on the basis of competition between bound species and a molecule (“the displacer”) that strongly binds to the column (Davies, WO 2009/135656).

Displacement chromatography is fundamentally different from other modes of chromatography in that the solutes are not desorbed in the mobile phase modifier and separated by differences in migration rates. In displacement mode, molecules are forced to migrate down the chromatogrpahic column by an advancing shock wave of a displacer molecule that has a higher affinity for the stationary phase than any component from the feed stream. This forced migration results in higher product concnetrations and purifites compared to other modes of operation (Spitali, WO2012/013682) . 

In dsplacement mode, the displacer binds at the top of the column and displaces any high affinity porduct/impurities bound in this region which then re-bind further down the column in turn displacing other species with a slightly lower affinity for the resin. This cycle of binding/displacement/re-binding continues down the chromatography column as more displacer is loaded and results in different species being resolved in to distinct bands which are then eluted from the column in reverse order of affinity (weakest binding first). The technique allows high loading concentrations of product (about 100g/L resin). Davies (WO2009/135656).

An example of a commercially avaialbe displacer molecule is Expell (SP1 (Sachem Inc., Texas, WO 2007/055896) and other potential displacer molecules are described in WO99/47574, WO 03074148 and WO963420).

Types of Chromatography used with Displacement Mode

Cation-exchange:

Torres (US5,028,696) discusses using displacement chromatography in a CEX column by the use of anionic displacers. 

Monoliths:

One area that should profit tremendously from the use of monolithic rather than particle based columns is displacemente chromatography. Other than in gradient elution, in displacement chromatography a certin distance is needed for the devleopment of the displacement train. (UNO Q and UNO S respectively). (Ruth, “Novel approaches to the chomatography of proteins” Biotechnoly and Bioprocessing/Biotechnol. Bioprocess. 27, 2003 455-502).

Paticular Types of Displacer Compounds/molecules

A displacer molecule should dissolve well in the mobile phase as high displacer oncentrations are required for fast and efficient separations. The molecule should be homogeneous, nontoxic, biocompatible, cheap and detectable. A polyion may be a displacer candidate for IEX. Small molecules have certain advantages over true polymers as protein displacers because they are more homogeneous and thus less likely to contain low affinity fracitons that may pollute the displacement train. Concomitantly, their separation from the protein zones is easier since the difference in size can be exploited (e.g., in gel filtraiton or dialysis). A problem is their inherently lower affinity, which can be ameliorated by either increasing the charge desnity or by introducing secondary nonspecific forms of interaction. (Ruth, “Novel approaches to the chomatography of proteins” Biotechnoly and Bioprocessing/Biotechnol. Bioprocess. 27, 2003 455-502). 

Examples of displacer molecules are disclosed in WO99/47574, WO03074148. 

Polyelectrolytes

The design and applicaiton of polyelectrolytic dispalcers requires good knowledge of the interaction between the charged molecules and the oppositely charged stationary phase surface. In addition to the predominant interaction mode, electrostatic in the case of ion exchange phases, a variety of secondary interactions may influence the displacer binding. (Schmidt J Chromatography A 1018 (2003) 155-167). 

Quaternary ammonium salts:

(Little, US2007/0102363) discloses a class of compounds known as organic quaternary ammonium salts (quat salts) which have advantages as displacer compounds. . Quat salts comprise positively-charged nitrogen atoms. 

Displacement of Particular Types of Proteins

Antibodies:

Wan (US13/803,808 and US9,067,990; US14/635,505 and US2015/0166653);  US14/079,076 and US9,017,687) teaches a method for producing a low acidic species comprising an antibody by contacting a first sample comprising the antibody with a chromatography media wehrein the antibody binds to the media, displacing the antibody with a displacing buffer comprising at least one displacer molecule and collecting the chromatography sample which comprising a composition of the antibody.

Gradient mode elution in combination with Displacement Separation

Martin (WO2006/116064) discloses a method for separating a target comound by injecting an overloaded amount of the sample into a chromatographic conduit thereby forming a displacement train in which the target compound is substantially separated and then flowing a solvent causing an eluent of the at least one target compound.