Chromatographic separation, modes affinity chromatography

Chromatographic separation of these mixtures in the elution mode is incapable of resolving many thousands of peptides present in these mixtures, even when orthogonal, two-dimensional separations are performed. The investigator is left with little option for low-abundance peptide iden-tihcation other than affinity approaches that target certain subclasses (e.g., phosphopeptides). While effective for certain applications, the latter allow for enrichment of only a small subset of low-abundance peptides. Because of its potential for broad applicability to the problem of low-abundance peptide enrichment, displacement chromatography remains a technique that offers great possibilities in this area. 

The separation column contains the stationary phase, while the mobile phase (frequently referred to as the carrier gas) is permitted to flow through this column from a pressurized gas cylinder (source of the mobile phase). The rate of mobile-phase delivery is controlled by a pressure and/or flow-regulating unit. An exclusive separation mode for the analytical GC is elution chromatography, in which the sample (a mixture of chemicals to be separated) is introduced at once, as a sharp concentration impulse (band), into the mobile-phase stream. The unit where sample introduction is performed is called the injector. The unfrac-tionated sample is transferred from the injector into the chromatographic column, where it is subjected to a continuous redistribution between the mobile phase and the stationary phase. Due to their different affinities for the... 

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