Polish J. Chem., 78, 1553–1565 (2004)

Parallel Electrode Processes in Absence of Supporting
Electrolyte. Further Strong Enhancement or Depression
of Transport of Ionic Species

by A. Nowicka(1), W. Hyk(1), Z. Stojek(1) and M. Ciszkowska(2)
(1)  Department of Chemistry, Warsaw University, ul. Pasteura 1, 02-093 Warsaw, Poland
E-mail: wojhyk@chem.uw.edu.pl; stojek@chem.uw.edu.pl
(2)  Department of Chemistry, Brooklyn College, CUNY, Brooklyn, NY 11210-2889, USA
E-mail: MalgCisz@brooklyn.cuny.edu

(Received January 27th, 2004)

Several ferrocene derivatives, including 1,1-ferrocenedimethanol, ferrocene, sodium ferrocenesulfonate, sodium ferroceneacetate and ferrocenylmethyltrimethylammonium hexafluorophosphate, were used to examine possible situations in voltammetry, if two of them are present together in the cell under the conditions of absence of supporting electrolyte.
The pairs of ferrocene derivatives were selected for the examination in such a way that one substrate was ionic and the other one neutral. Also, the diffusion coefficients of the species in the solution were sufficiently similar to avoid the effect of nonadditive voltammetric currents. If the ion formed from the neutral substrate and the second ionic substrate are the key ions in the process of preserving the electroneutrality in the diffusion layer at the electrode surface, a significant enhancement or depression of the transport of the ionic substrate takes place. The corresponding wave heights are either much higher (different signs of the ion charges) or lower (identical signs), compared to a situation, where the ionic substrate is present alone in a solution with no supporting electrolyte.
The sequence of voltammetric waves of the two substrates determines, which wave is actually affected. The situations demonstrated in the paper may be useful in analytical strategies, aiming at enhancing or depressing a particular voltammetric signal.