The evolution of sol-gel technology and organically modified ceramic materials created new possibilities for electroanalytical sensors. Lev and coworkers introduced a new class of sol-gel derived composite carbon ceramic electrodes (CCE). One of the ways of modification of CCE with large number of redox groups is impregnation with redox probe solution in hydrophobic polar solvent.
The CCE modified with redox probe (ferrocene, t-butyloferrocene or decamethyloferrocene) solution in hydrophobic polar solvent (nitrobenzene, 2-nitrophenyloctylether or 2-nitrodiphenylether) was prepared and studied. The electrode material was obtained by sol-gel process. It consists of the graphite powder homogeneously dispersed in hydrophobic silica matrix based on methyltrimethoxysilane. After drying and gelation, the electrode was immersed in modifier solution. The electrochemical properties of the electrode were investigated in aqueous salt solution. The features of cyclic voltammetry curves: stability, peak current magnitude, shape and midpeak potential corresponding to the redox reaction depend on the redox probe, organic solvent and the salt present in aqueous phase. The redox probe is easier to oxidize in the presence of less hydrated anions. The magnitude of peak current is proportional to concentration of salt in aqueous phase.
The electrooxidation of redox probe dissolved in hydrophobic solvent present within pores hydrophobic silicate matrix is followed by anion transfer from aqueous phase, with simultaneous redox active cation transfer to the aqueous phase. The contribution of both reactions phase depends on the type of redox probe, the type of electrolyte and its concentration. The electrode process occurs at the three phase junction formed by graphite particle and liquid organic-aqueous interface supported by hydrophobic silicate matrix. The studied electrode may become attractive sensors on the redox inactive anion present in aqueous phase.