Propagating behavior comparison of analytes and background electrolytes in a concentration polarization process

Abstract

Concentration polarization (CP) is an electrochemical phenomenon related to the concentration gradient (under a transversal electric field) near an ion selective membrane surface. During concentration polarization process, quantitatively investigate the background electrolyte (BGE) concentration distribution is a very challenging problem. In this study, we conducted transient simulations within 2D micro-nanochannel domain to capture the dynamic nature of concentration polarization process and compared the propagating behavior of analytes and BGE. The simulation results show that the depletion area of chloride ion and analyte are both increase with time at ohmic and limiting region. The normalized depletion area (NDA) differences increases with decreasing BGE concentration. For the high applied voltage (overlimiting region), chloride ion and analyte at the anodic side microchannel are depleted everywhere that the NDA tends to 1 after an increasing step because of the electroconvection effect. This means there is no depletion area (DA) differences between two species in this plateau region. These results tell us the fluorescent ion indicator can’t show the exact BGE concentration distribution during CP process and we need to find new technique to visualize the concentration field.