Editing Chromatography (section)

==Displacement chromatography==
The basic principle of [[displacement chromatography]] is:
A molecule with a high affinity for the chromatography matrix (the displacer) competes effectively for binding sites, and thus displaces all molecules with lesser affinities.<ref>[http://www.sacheminc.com/industries/biotechnology/teaching-tools.html Displacement Chromatography 101] {{webarchive |url=https://web.archive.org/web/20080915113736/http://www.sacheminc.com/industries/biotechnology/teaching-tools.html |date=15 September 2008 }}. Sachem, Inc. Austin, TX 78737</ref>
There are distinct differences between displacement and elution chromatography. In elution mode, substances typically emerge from a column in narrow, Gaussian peaks. Wide separation of peaks, preferably to baseline, is desired for maximum purification. The speed at which any component of a mixture travels down the column in elution mode depends on many factors. But for two substances to travel at different speeds, and thereby be resolved, there must be substantial differences in some interaction between the biomolecules and the chromatography matrix. Operating parameters are adjusted to maximize the effect of this difference. In many cases, baseline separation of the peaks can be achieved only with gradient elution and low column loadings. Thus, two drawbacks to elution mode chromatography, especially at the preparative scale, are operational complexity, due to gradient solvent pumping, and low throughput, due to low column loadings. Displacement chromatography has advantages over elution chromatography in that components are resolved into consecutive zones of pure substances rather than "peaks". Because the process takes advantage of the [[Nonlinear system|nonlinearity]] of the isotherms, a larger column feed can be separated on a given column with the purified components recovered at significantly higher concentrations.