ABSTRACT
Elution behaviour of polystyrene (PS) and poly (methyl methacrylate) (PMM) on Shperosil in many different eluents and its de pendence upon solvent goodness, as defined by the a exponent of the Mark-Houwink eq., with solvent strength (ε°), with flow rate and with molecular size has been studied. The application of a network-limited partition and adsorption mechanism allows the evaluation of relative distribution coefficients (Kp) with reference to a standard state, this being any good solvent eluent system.
Low Kp values are obtained, with PS as a solute, at high ε° eluent values, partition being mainly responsible. At low ε° values, adsorption effects contribute to the high Kp values besides parti tion. An increase in flow rate results on a decreasing in retention, this effect being more evident the higher adsorption contributions are. Similar trend is also observed when lowering the molecular weight down to the oligomer region: partition not being apparently affected by molecular size, while adsorption seems to diminish in the lower molecular weight region.
In general PMM follows the above elution trend, its elution curves being always shifted to higher retention volumes than those of PS, probably due to adsorption effects.
