Potentiometric detection of ascorbate using a graphite carbon electrode

A graphite carbon electrode was used for the potentiometric detection of ascorbate. The electrode exhibits a linear response with a slope of - 42 +/- 1.0 mV decade(-1) in concentrations ranging from 5 x 10(-4) to 5.0 x 10(-2) M in 0.1 M NaOH solution with a detection limit of 5.0 x 10(-6) M. The response mechanism of this electrode was investigated by potentiometry, voltammetry, and scanning electron micoscropy (SEM), and it suggests that the electrode potential change resulted from the ion-exchange adsorption and subsequent oxidation of ascorbate on the electrode surface at pH 12-13. The electrode exhibits high sensitivity, selectivity and reproducibility. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.