Electrocatalysis and amperometric detection of ethanol at ruthenium-based inorganic films with improved response stability

A glassy carbon electrode coated with a thin film of mixed-oxidation state ruthenium oxide cross-linked with ruthenium cyanide is used for the electrocatalytic oxidation of ethanol in acidic media. This inorganic redox film offers attractive features for application as an electrocatalytic amperometric sensor in batch and flowing solutions. The ruthenium-based modified glassy carbon electrode was assembled in a thin-layer electrochemical cell, and the stability of the film was evaluated. For constant-potential amperometric detection (+ 1.05 V vs. AgAgCl) in flow injection analysis, substantial improvements in the response stability of the film were obtained using carrier electrolytes spiked with 5 × 10−6 M of each of the electroplating salts, i.e., RuCl3 and K4Ru(CN)6. Under optimal experimental conditions the peak current response increases linearly with ethanol over the range 0.1–10 mM; linear least squares fit of the data (n = 7) yielded a slope of 0.601 ± 0.003 μA mM−1 (95% confidence limits) with a correlation coefficient of 0.99995.