DIFFERENTIAL CYCLIC VOLTFLUOROMETRY AND CHRONOFLUOROMETRY OF THE TRANSFER OF FLUORESCENT IONS ACROSS THE 1,2-DICHLOROETHANE-WATER INTERFACE

The time derivative of fluorescence vs time curves recorded with voltage-scan fluorometry (Kakiuchi, T.; Takasu, Y.; Senda, M. Anal. Chem, 1992, 64, 3096-3100) for the transfer of the divalent anionic form of Eosin B (EB) across the 1,2-dichloroethane-water interface gives curves isomorphic to the cyclic voltammograms of ion transfer of EB when the concentration of EB in the aqueous phase is in the micromolar range or lower. From the differential cyclic voltfluorograms obtained, electrochemical properties of ion transfer, e.g., the Gibbs energy of transfer of fluorescent ions and the reversibility of ion transfer, can be estimated at the nanomolar level, which is similar to 5 orders of magnitude more sensitive than conventional cyclic voltammetry of the ion transfer. Chronofluorometry, i.e., the potential-step transient of the fluorescence for the transfer of fluorescent ions, is demonstrated to be utilized as a counterpart of the chronocoulometry of ion transfer in the same low concentration range.