Platinum black coated microdisk electrodes for the determination of high concentrations of hydrogen peroxide in phosphate buffer solutions.
The performance of a series of platinum black coated microdisk electrodes (Pt-Bs) was investigated in H(2)O(2) solutions over the concentration range 0.1-500mM, in phosphate buffer media pH 7. The Pt-Bs were prepared by electrodeposition of Pt onto the surface of microdisk electrodes 12.5mum of nominal radius, from aqueous solutions containing hexachloroplatinic acid. The resulting roughness factors (RF, i.e., the ratio of the effective surface area to the geometric electrode area) varied between about 10 and 100. The voltammograms recorded with these electrodes, at relatively low H(2)O(2) concentrations (up to 50-100mM), displayed rather steep mixed anodic-cathodic waves, which attained well-defined and stable current plateaus. At the higher hydrogen peroxide concentrations, additional waves both in the anodic and cathodic region or dramatic current drop phenomena were observed. The wave split phenomenon was attributed to the insufficient buffering capacity of the base electrolyte solution within the pores of the platinum black, induced by the large amounts of hydrogen ions produced in the oxidation process. The current drop was attributed to either the formation of oxygen bubbles, which limit diffusion of H(2)O(2) down the pores, or saturation of the active sites responsible for the decomposition of H(2)O(2) to O(2) and H(2)O. The H(2)O(2) concentration at which the above phenomena occurred depended either on the phosphate buffer concentration in the bulk solution or the RF factor of the electrodes. The latter conditions also affected the dynamic range of detection, the sensitivity and low detection limits. Advantageous analytical characteristics were obtained with a Pt-B of RF of about 24, which provided a dynamic range between 0.5 and 230mM, a sensitivity of 1.93(+/-0.06)AM(-1)cm(-2) and a low detection limit of 0.05mM. The reproducibility was also very good, it being within 2-3%. The usefulness of the Pt-Bs for real samples analysis was tested in an antiseptic solution containing large amounts of H(2)O(2).
Kicela
Aleksandra
A
Department of Physical Chemistry, University of Venice Calle Larga, S. Marta 2137, 30123 Venice, Italy.
Daniele
Salvatore
S