Alternative Modes of Displacement Chromatography

In contrast to high molecular weight polyelectrolyte displacers, the efficacy of low molecular weight displacers is dependent on both mobile phase salt and displacer concentrations. This sensitivity to the operating conditions opens up the possibility of carrying out selective displacement where the products of interest can be selectively displaced, while the low affinity impurities can be desorbed in the induced salt gradient ahead of the displacement train and the high-affinity impurities either retained or desorbed in the displacer zone.43 A 

FIGURE 8 Displacement histogram and UV detector trace for a selective displacement process. (A) Displacement separation of a three-component protein mixture using streptomycin sulfate A as a displacer. Column 100 X 5 mm i.d. strong cation exchange (8 m) carrier 30 mM sodium phosphate buffer, pH 6.0 feed 1.6 mL of 0.392 mAI ribonudease A, 0.42 mM horse cytochrome c and 0.34 mM lysozyme in the carrier. Total column loading 12.7 mg/mL column displacer 25 mM streptomycin sulfate A flow rate 0.2 mL/min fraction size 200 /iL. (Kundu et al.43) (B) UV detector trace monitored at 280 nm for the displacement separation shown below. 

FIGURE 9 Displacement chromatography on a retained pH gradient. The presaturation and elution buffers are formed by titrating 0.05 M NaOH with MOPS and acetic acid, respectively. Adsorbent TosoHaas TSK Q-5PW (5 /x particles) flow rate 0.1 mL/min proteins /3-lactoglobulins A and B (from Narahari et a/.,69 with permission from Elsevier Science). 

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