A numerical scheme is developed to simulate electro-osmotic flow and mass transport in a microchannel which includes a 180° tu. The model has been used to predict the behaviour of electro-osmotically driven flows. The detailed structure of the flow field in a microchannel in combination with species mass diffusion can explain the concentration dispersion introduced by a 180° tu. The results of our simulations agree both qualitatively and quantitatively observation.It is demonstrated that an improved electro-osmotic force model could simulate the with experimental electrokinetically driven flow well without making detailed calculations of the electric charge density distribution within the electrical double layer. Additionally, because this model applies forces to the liquid as opposed to imposing local velocities, it should also be appropriate for use where pressure gradients exist in the flow field.