Effect of ligand protonation on the facilitated ion transfer reactions across oil|water interfaces. III. Digital simulation and experimental approach

In a previous paper (S.A. Dassie, J. Electroanal. Chem. 578 (2005) 159), we have presented the general equations for a model of ion transfer reactions across the oil|water interface assisted by a neutral protonatable ligand. The model was solved using Laplace transforms. The analysis was mainly focused on the effect of water autoprotolysis on the transfer processes. In the present work, the model for the protonatable species transfer is solved using explicit finite difference. The use of this method to solve the system is mainly intended to obtain information regarding the concentration profiles away from the interfacial plane and to take account of different diffusion coefficients for each species involved in the transfer mechanism. The model is corroborated by the experimental results for the quinine transfer across the H2O|1,2-dichloroethane interface, and the corresponding transfer mechanism is analysed in terms of the current-potential and concentration profiles obtained from the digital simulations.