Cation‐Specific Electrokinetic Separations Using Prussian Blue Intercalation Reactions

Abstract

We report a new approach for forming ion depletion zones (IDZs) using intercalation reactions at an electrochemically controlled Prussian blue (PB) film. The experiments described here were performed using a microfluidic device, wherein a charged fluorophore in solution was used as a proxy to monitor IDZ formation. In the presence of K + , intercalation reactions proceed readily to form an IDZ, and thus enrich the fluorophore up to 37-fold. In the presence of the larger hydrated Li + or tetrabutylammonium (TBA +) ions, however, ion intercalation proceeded less quickly than with K +. Slower ion intercalation resulted in a weaker IDZ and correspondingly lower enrichment factors of eight-and six-fold, respectively. These results are significant because they show that PB intercalation reactions selectively form an IDZ. Accordingly, we anticipate that these findings will lead to a better understanding and further interesting applications of intercalation materials like PB for efficient and selective enrichment and separations.

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

“…Second, these experiments were performed using a 20.0 V driving voltage instead of 40.0 V. A lower driving voltage is associated with less significant enrichment factors because the sequestering forces responsible for enrichment are lowered (i. e., decreased migration and EOF, as well as a smaller applied counterforce from PDF). In turn, the analyte band broadens and the resulting enrichment factors are lower [48–50] …”