Regular Irregularity in the Transfer of Anionic Surfactant across the Liquid/Liquid Interface

Irregular current spikes and other anomalies seen in voltammetry of the transfer of anionic surfactants, alkyl sulfonates, and alkyl sulfates across the 1,2‐dichloroethane/water (DCE/W) interface are reproducible. The anomalies have a certain regularity that is predicted by a recently proposed concept, the electrochemical instability. Irregular current spikes follow after the augmentation of the current induced when the phase‐boundary potential is brought close to the mid‐point potential of the transferring surfactant ions. Potential‐step chronoamperometry clearly demonstrates the presence of the instability window, that is, the potential region where the interface becomes unstable only in the limited range of the phase‐boundary potential. Electrochemical instability of the liquid/liquid interface has been demonstrated in regular irregularity of cyclic voltammograms and chronoamperometry transients (as shown in the graphic) in the presence of the potential‐dependent adsorption and interfacial transfer of surfactant ions. The instability zone exists as a window in the potential range around the half‐wave potential of the ion transfer.