Enriching Cations Using Electric Field Gradients Generated by Bipolar Electrodes in the Absence of Buffer.

We report that ionic current gradients and corresponding electric field gradients formed at bipolar electrodes are useful for enriching cations up to ∼350‐fold at specific locations in microfluidic devices. The enrichment mechanism is determined by collecting current data, measuring solution conductivity, and by performing pH indicator experiments. These data reveal the dynamic nature of the enrichment mechanism. Specifically, they show the complex relationship between the ionic current gradients formed at the bipolar electrode and the extent of cation enrichment. Finally, we demonstrate cation enrichment is possible in buffer‐free solutions containing up to 50.0 mM KCl. This finding is significant because it broadens the range of solutions in which membrane‐free, electrochemical separations using bipolar electrodes can be performed. [ABSTRACT FROM AUTHOR]