Study of facilitated potassium ion transfer across a water ∣ 1,2-dichloroethane interface using different phase volume ratio systems

A study of potassium ion transfer across a water ∣ 1,2-dichloroethane (W ∣ DCE) interface facilitated by dibenzo-18-crown-6 (DB18C6) with various phase volume ratio systems is presented. The key point was that a droplet of aqueous solution containing a redox couple, Fe(CN)63−/Fe(CN)64−, with equal molar ratio, was first attached to a platinum electrode surface, and the resulting droplet electrode was then immersed into the organic solution containing a hydrophobic electrolyte to construct a platinum electrode/aqueous phase/organic phase system. The interfacial potential of the W ∣ DCE within the series could be externally controlled because the specific compositions in the aqueous droplet make the Pt electrode function like a reference electrode as long as the concentration ratio of Fe(CN)63−/Fe(CN)64− remains constant. In this way, a conventional three-electrode potentiostat can be used to study the ion transfer process at a liquid ∣ liquid (L ∣ L) interface facilitated by an ionophore with variable phase volume ratio (r=Vo/Vw). The effect of r on ion transfer and facilitated ion transfer was studied in detail experimentally. We also demonstrated that as low as 5×10−8 M DB18C6 could be determined using this method due to the effect of the high phase volume ratio.