DETERMINATION OF ASCORBIC-ACID USING AN ORGANIC CONDUCTING SALT ELECTRODE

An organic conducting salt electrode (based on tetrathiaful-valene-p-tetracyanoquinodimethane) was used for the amperometric determination of ascorbate levels in aqueous samples. The current/concentration relationship was linear up to approximately 50 mM ascorbate at -100 mV (Ag/AgCl). At more oxidizing potentials (-75 and -50 mV), the signals were larger, but the linear dependence evolved into a square root dependence at approximately 2.5 mM ascorbate. Steady-state signals were obtained within 10 s. Optimum results were obtained between pH 7.5 and 9.0 and at high buffer concentrations. The TTF-TCNQ electrode was used to determine the ascorbate content of apple juice. The data were in reasonable agreement with results from a spectrophotometric-based commercial test kit. Neither adsorption nor background reductant interferences were observed using a membrane electrode. Sulfite and dopamine are not electrooxidized by the electrode at -75 mV and therefore are not interferents.