EOF in monolithic poly(styrene-co-divinylbenzene) capillary columns

In this paper, we present the result of our study on generation of EOF on uncharged poly(styrene-co-divinylbenzene) -based monolithic capillary columns. Three types of neutral monoliths were used: unmodified poly(styrene-co-divinylbenzene) and two modified with octadecyl chains: using grafting process or Friedel-Crafts reaction. The electroosmotic mobilities (mu(epsilon OF)) versus pH profiles are compared, as well as molecular modeling using HyperChem software was employed to describe the observed phenomena. The mu(epsilon OF) was almost independent of pH when pH was increased from 2.5 to 9.5 during the consecutive experiments; however, it decreased significantly when pH was decreasing between these values. The modeling has shown that the buffer molecules call be attracted by the neutral polystyrene surface only in the presence of water molecules, thus creating a negatively charged layer.