TOWARDS PREDICTING MOBILITY AND RESOLUTION IN POLYMERIC MEDIA - SOME FIRST STEPS

Particle size-dependent retardation (''molecular sieving'') in electro phoresis can be achieved in polymer solutions or gels. In the semidilu te concentration range of polymer solutions, mobility of ''rigid, sphe rical'' particles can be predicted from their size (in the size range less than 20 nm radius), the screening length specific for the particu lar polymer and a constant that can be experimentally determined for a polymer. That constant could be universal for all hydrophilic uncharg ed polymers. Band spreading in polymer solutions is constant over a ra nge of particle sizes and polymer concentrations and increases beyond that range. Presumably the critical division between the two ranges oc curs when the diameter of the particle exceeds the screening length of the polymer network. Resolution, defined as separation divided by the sum of bandwidths, can thus be predicted for a limited particle size and polymer concentration range. In gels, resolution can be estimated from the slopes and free mobility intercepts of the Ferguson plot. How ever, the previous computation of resolution needs to be revised in vi ew of the fact that band spreading in gels proceeds in proportion to t ime, presumably through interaction with the polymer, and not as a fun ction of the square root of time as would be the case if band spreadin g resulted from diffusion.