DISPLACEMENT CHROMATOGRAPHY WITH ON-COLUMN ISOMERIZATION

Displacement chromatography was simulated for the separation of two fe ed components interconverting by a reversible first order reaction and with Langmuirian adsorption behavior. The study was prompted by recen t interest in the isolation of cis and trans forms of peptides contain ing one or more peptidyl-proline residues when the isomerization react ion interferes with the separation. The parameter values used in the s imulations are similar to those found experimentally by reversed-phase chromatography and capillary electrophoresis of phenylalanine-proline dipeptide. From the concentration profiles computed by the finite dif ference scheme, the dependence of both the yield and production rate o n the temperature, column length, flow velocity and displacer concentr ation was evaluated. The most important operational variable of the sy stem is the temperature as it affects both the kinetic and adsorption parameters. The yield and production rate of the component of interest were evaluated as a function of the column length and displacer conce ntration under conditions that facilitate its efficient separation and the plots show an optimum. Nonetheless, optimal conditions for yield and production rate were considerably different. In the temperature ra nge from 2 to 42 degrees C, the yield always decreases with increasing temperatures and for all the cases, optimum yield by displacement man dates the use of conditions such as pH, solvent and temperature under which the rate of interconversion is reduced to a level where it does not palpably interfere with the separation. On the other hand, under c ertain conditions optimal production rate can be obtained at higher te mperatures. (C) 1997 Elsevier Science B.V.