THE INFLUENCE OF LEAD UPD ON THE OXIDATION OF GLUCOSE AT PLATINUM-ELECTRODES - AN ELECTROCHEMICAL QUARTZ-CRYSTAL MICROBALANCE STUDY

The oxidation of glucose at Pt electrodes covered with upd deposits of Pb in acid media has been investigated using the electrochemical quar tz crystal microbalance (EQCM). Glucose alone has a small effect on th e mass response but changes in upd Pb coverage have a large effect. Th is allows changes in upd Pb coverage to be followed easily despite the fact that the associated current is largely obscured in the cyclic vo ltammogram. Cyclic voltammetry at low glucose concentrations shows a m ultiple peak structure in the double layer region of potential at low upd coverages that is changed to the more familiar single peak as upd coverage increases. Mass responses also reveal some blockage of Pb upd by glucose or species derived from it during cyclic voltammetry. Data from mass transients show that the deliberate formation of poisons pr ior to addition of Pb2+ ions to the electrolyte results in a substanti al suppression of upd coverage especially between -0.1 and 0.1 V (see) . Finally, mass transients accompanying injections of Pb2+ in the pres ence of glucose in the electrolyte reveal the suppression of adsorptio n of Pb2+ cations on an oxidised Pt surface by species derived from gl ucose.