ON THE SELECTIVITY OF ADSORPTION CHROMATOGRAPHY

In this paper, the shape of chromatograms obtained by elution of copol ymers with a mixture of solvent-nonsolvent of variable composition has been studied from a theoretical point of view. It is assumed that the thermodynamic quality of the mixture at which the copolymer is eluted depends only on its composition and not on its mass and structure. If one characterizes the polydispersity in composition, assuming that ea ch constituent obeys a molar mass distribution of the Zimm-Schulz type , one can draw the following curves: concentration of the copolymer ve rsus eluant composition. They depend on three parameters, including co mposition of the copolymer and the polydispersity of each constituent. The most striking result is that the shape of the chromatogram change s dramatically when one increases the polydispersity of either constit uents. For low polydispersities, one obtains a classical peak. For lar ge polydispersities, the chromatogram has a minimum for the intermedia te values of composition and presents peaks in the vicinity of the pur e homopolymers. This can be explained easily by a qualitative argument . (C) 1996 John Wiley & Sons, Inc.