A voltammetric methodology to determine the standard Gibbs energy of transfer of highly hydrophobic and hydrophilic ions has been developed. The electrochemical cell used includes a water|1,2-dichloroethane micro-interface supported on a microhole in a thin polymer film separating an electrolyte-free aqueous phase and an organic phase with an electrolyte at low concentrations. The limiting current and the half-wave potential of these organic ions were determined by fitting the initial part of the ion transfer wave. The methodology was validated using ions with known thermodynamic data, and applied to very hydrophobic and very hydrophilic ions that usually cannot be observed within the potential window.