Ion transfer of weak acids across liquid | liquid interfaces

• General equations for half-wave potential of ion transfer of weak acids across liquid | liquid interfaces are developed.
• Ion pairing and non-ideal electrolyte solutions are explicitly incorporated into the model.
• Simple criteria to evaluate the presence of ion-pairs and to calculate the apparent ion-pair formation constants are included.

The main purpose of this paper is to develop a model for the ion transfer of weak acids across liquid | liquid interfaces including ion pairing and non-ideal electrolyte solutions to calculate the half-wave potential. The main equation derived in this model allows the simulation of different chemical systems, comprising multiple acid-base equilibria, hydrophilic and hydrophobic neutral weak acids, and different anions, including ion-pair formation in the organic phase. Hence, several representative chemical systems are analysed in detail in order to demonstrate the usefulness of the model. In addition, simple criteria to evaluate the presence of ion-pairs in the organic phase as well as the calculation of the apparent ion-pair formation constants are included.

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