Sample dispersion due to buffer disturbances and zeta potential variability in electroosmotic microchannel flows

This paper presents detailed simulations to study analyte dispersion in electroosmotic microchannel flow. We focus on electrokinetic and hydrodynamic dispersion caused by buffer disturbances and random zeta potential variability. A two-dimensional microchannel model is used that considers the coupled momentum, species transport, and electrostatic field equations, including a model for the dependence of the zeta potential on pH and buffer molarity. The chemistry model accounts for pH-dependent protein labeling reactions as well as detailed buffer electrochemistry in a mixed finite-rate/equilibrium formulation. The model also has the unique capability to account for uncertainty in input parameters, such as species mobilities, as well as for stochastic processes, such as random zeta potential variability. These uncertainties and variabilities are handled using polynomial chaos representations for model inputs and field quantities. The results show a strong increase of analyte dispersion for increasing species charge number and for increasing zeta potential variability.