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 volta ge-scan fluorometry (Kakiuchi, T.; Takasu, Y.; Senda, M. Anal. Chem, 1 992, 64, 3096-3100) for the transfer of the divalent anionic form of E osin 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 o r lower. From the differential cyclic voltfluorograms obtained, electr ochemical properties of ion transfer, e.g., the Gibbs energy of transf er of fluorescent ions and the reversibility of ion transfer, can be e stimated at the nanomolar level, which is similar to 5 orders of magni tude more sensitive than conventional cyclic voltammetry of the ion tr ansfer. Chronofluorometry, i.e., the potential-step transient of the f luorescence for the transfer of fluorescent ions, is demonstrated to b e utilized as a counterpart of the chronocoulometry of ion transfer in the same low concentration range.