Comparison of Ion Transfer Thermodynamics at Microfluidic and Droplet-Based Three Phase Electrodes

Highlights: • Ion transfer processes at microfluidic three phase electrodes were studied. • The voltammetric peak potentials depend on ion hydrophobicity and concentration. • The model developed for droplet based systems can be used also in microfluidics. • The volumetric flow rate does not affect the recorded peak potentials. • Gibbs energies of ion transfer from water to N-octyl-2-pyrrolidone were determined. - Abstract: We have investigated whether the thermodynamic model developed for ion transfer processes across the liquid|liquid interface at a droplet-based three phase electrode (TPE) can be applied to a microfluidic system. We have compared effect of ion transfer potential and ion concentration on the voltammetric peak potential recorded at droplet and microfluidic TPEs. The results were analyzed in terms of the Nernst-like equation derived for droplet TPE. As a model reaction, electrooxidation of decamethylferrocene coupled to anion transfer from aqueous electrolyte solution to N-octyl-2-pyrrolidone (NOP) has been chosen. We have found that both ion effect and concentration effect are the same in the two systems and agree with the Nernst equation. This allows microfluidic TPEs to be used in electroanalysis. Additionally, Gibbs energies of transfer for different inorganic anions have been determined for the studied NOP water biphasic system