Authors: J.J. Feng, S. Krishnamoorthy, S. Sundaram, R. Bhardwaj and J.G. Santiago
Affilation: CFD Research Corporation, United States
Pages: 234 - 237
Keywords: sample stacking, modeling, dispersion
In this paper we developed a numerical simulation method that solves the transport phenomenon associated with sample stacking in microchip-based separation system. The model is based on thin double layer approximation where the electrostatic force is only pronounced in a very thin layer adjacent to the charged surface. The electrokinetic equations describing the electrophoresis as well as electroosmosis are solved numerically in conjunction with fluid flow, heat transfer and electrostatics. The entire theory is applicable to both fully ionized electrolyte solutions as well as acid, base and ampholyte solutions in which rapid association and dissociation of species may occur. We studied a typical sample stacking with one interface in the presence of electroosmosis. The evolution of sample peak grows almost linearly, which is in consistence with experiment observation Sample dispersion due to mismatch of EOF flow in sample and buffer region is also examined, where two interfaces are involved. This configuration represents a typical FASS protocol in which anions accumulate at the interface near anode and cations accumulate in the other direction. The mismatch of EOF flow creates internal pressure which disperses the sample plug, thus reduces the resolution of sample profile. The current simulation results agree qualitatively with experimental results.