Finite-Volume Methods for Isotachophoretic Separation in Microchannels

Abstract

Numerical simulation results are obtained for isotachophoresis (ITP) in two-dimensional (2-D) straight microchannels. This 2-D ITP model is formulated based on finite-volume schemes using five ionic components: one leader, one terminator, two samples, and a counter-ion electrolyte. Distinct mobilities and diffusion coefficients are assigned to all ionic components, and an electric field is maintained along the channel to carry out the electrophoretic separation in the microchannel. The computer model is developed to solve the mass and charge conservation equations and to satisfy electroneutrality condition in the system. Three different finite-volume schemes, power-law, hybrid, and upwind, are tested to obtain the best numerical solution of this nonlinear electrophoretic problem. The normalized standard deviation technique is introduced to evaluate the performance of these three schemes. Numerical results show that the power-law scheme performs better; grid Peclet numbers up to 23 are acceptable for this nonlinear isotachophoresis. The effects of the applied electric potential, ionic mobilities and initial distribution of samples on the separation behavior are also presented.

This investigation was supported in part by the Washington State University Office of Research and in part by the National Science Foundation under Grant CTS0300802.