A.c. voltammetric evidence for the transient adsorption of asymmetric ions in the transfer across the nitrobenzene¯water interface

A.c. impedance studies of the ion transfer have evidenced the transient adsorption of xanthene-type anions and other ions having asymmetric charge distribution at the nitrobenzene¯water interface. The phase angle of the charge transfer admittance becomes smaller than unity at the potentials beyond the midpoint potential of the ion transfer. This anomaly does not appreciably depend on the sign of the ionic charge or the location of the midpoint potential, as predicted by the theory proposed recently based on the thermodynamic reasoning of the adsorption and ion partitioning of surface active ions in electrochemical liquid¯liquid two-phase systems [T. Kakiuchi, J. Electroanal. Chem. 496 (2001) 137].