Determination of alkali metal ion transfers at liquid vertical bar liquid interfaces stabilized by a micropipette

作者：Stockmann Tom J; Montgomery Anne Marie; Ding Zhifeng^*

来源：Journal of Electroanalytical Chemistry, 2012, 684: 6-12.

DOI：10.1016/j.jelechem.2012.08.013

• Liquid vertical bar liquid electrochemistry
• Simple ion transfer
• Formal transfer potential
• Alkali metal ions
• Micropipette

The extremely stable microinterface between two immiscible electrolytic solutions (micro-ITIES) housed at the tip of a 25 mu m diameter capillary, has given access to simple ion transfer of alkali metal ions for the first time at conventional supporting electrolyte concentrations (similar to 5 mM). This was made possible by a uniquely designed pipette holder that uses a syringe to back-fill the aqueous phase and also helps to adjust and maintain the ITIES at the capillary tip, which was continuously monitored using a CCD camera attached to a custom-designed microscope. The formal transfer potential, Delta(w)(o)phi(o')(iz), for each of the ions (Li+, Na+, K+, Rb+ and Cs+) was determined by means of cyclic voltammetry along with differential pulse voltammetry. This thermodynamic constant is of great value as a point of reference for the quantitative evaluation of metal ion extraction through interfacial complexation at an ITIES. Since these ions typically limit the polarizable potential window, in the past Delta(w)(o)phi(o')(iz), was estimated using the current-potential response at the edge of the voltammogram, a method developed through numerical calculations. Delta(w)(o)phi(o')(iz), was also determined at a microhole ITIES, requiring minimal concentrations of the analyte and no supporting electrolyte.

• 出版日期2012-9-15