Self-focusing in gradient liquid adsorption chromatography of polymers

We point out the specificities of the separation process at work during liq uid chromatography of polymers in a gradient of composition of the eluent. Tile main feature is that, after a transient regime, the concentration prof ile tends to move as a front, i.e., without diffusive spreading in time. Th is results in relatively sharp peaks and the uselessness of long columns. W e propose a simple analytical model for this self-focusing process that all ows us to anticipate optimal conditions of operation. This analysis is supp orted by experimental tests.