When an ionizable solute, B(org), is present in an ITIES electrochemical cell, it may spontaneously partition between aqueous and organic phases according to its aqueous acid dissociation constant Ka, partition coefficient P, and the pH of the aqueous phase, complicating kinetic analysis. When neutral and ionized forms of B(org) are distributed between the two phases, the application of a Galvani potential difference Δ 𝑜𝑜 𝑤𝑤 𝜙𝜙 across the interface may drive the i) direct transfer of H+(aq) to B(org) across the phase boundary, ii) transfer of the conjugate acid BH + (aq) (as a minority species previously partitioned to the organic phase), iii) shuttling via an interfacial-sequential pathway, or all processes simultaneously (Figure ). Since there are multiple possible processes responsible for the observed current, it is important understand if and how the measured 𝑘𝑘 0 can be understood in terms of molecular interfacial proton-transfer kinetics and mechanisms.