Liquid adsorption chromatography with a continuous solvent gradient elution
has been shown by several authors to often separate random and graft copol
ymers according to their chemical composition whereas their molar masses do
not play an important role. A tentative explanation of this finding is pre
sented. It is assumed that the copolymer species travel along the column wi
th a velocity which exactly corresponds with that of the eluent composition
, exhibiting a displacing power just necessary to prevent a fast progress o
f the macromolecules due to their exclusion. Under specific circumstances,
retention of macromolecules at this adsorption promoting "barrier" depends
almost exclusively on the copolymer composition and not on its molar mass.
This hypothesis is based on the mechanism of the recently proposed and test
ed liquid chromatographic elution of homopolymers under limiting conditions
of desorption and takes into account the simultaneous effect of adsorption
and exclusion of macromolecules onto/from the column packing.