Experimental artifacts associated with impedance measurements at liquid—liquid interfaces

Characterization of doping and electropolymerization of free standing films of polyterthiophene

“…At low frequencies, undesired ion transfer is observed in the potential window of study [34]. Ideal polarization is in fact never established in L/L systems.…”

“…They showed the artifact was strongly related to the position of the interface, decreasing when the interface approached the Luggin capillary of the organic phase. The artifact also appeared when the organic reference arm resistance was large [34]. Hence, the artifact was associated with the uncompensated resistance of the organic phase, as well as to the resistance of the organic Luggin capillary.…”

“…Herrmann et al [32] overcame this problem by adding a metal wire that responds at high frequencies, a technique then used by Samec et al [27]. Another approach was reported by Cahan et al [33] and adapted to L/L interfaces [34,35]. The idea was to reduce the resistance of the organic phase in the reference capillary, using a ''Lugging-less'' cell [36].…”

“…Silva and Moura [36] concluded it was caused by a geometrical capacitance of unknown origin, associated with the cell design. Wiles et al [34] tested different cells for a number of electrodes and geometries. They showed the artifact was strongly related to the position of the interface, decreasing when the interface approached the Luggin capillary of the organic phase.…”

“…Hence, the artifact was associated with the uncompensated resistance of the organic phase, as well as to the resistance of the organic Luggin capillary. These formed an unwanted RC filter with stray capacitance on the leads [34,37]. The effect could be minimized by proper cell design [34] or by improved instrumentation [38].…”