Voltammetric Determination of Glucose at Bismuth-Modified Mesoporous Platinum Microelectrodes.

Mesoporous platinum microeletrodes (MPtEs) modified by a mono- or submonolayer of adsorbed bismuth (Bi- MPtE) were investigated and employed for the detection of glucose in 0.2 M NaOH solutions. The mesoporous platinum films were electrodeposited from hexachloroplatinic acid dissolved in the aqueous domain of the lyotropic liquid crystalline phase of octaethylene glycol monohexadecyl ether. Bismuth ad-atoms were obtained by under potential deposition of Bi3þ ions in 0.5 M H2SO4 solutions. The coverage of the MPtEs by irreversibly adsorbed bismuth was checked in either a 0.5 M H2SO4 or 0.2 M NaOH solution free of Bi3þ ions, and exploiting the charge involved in the hydrogen adsorption/desorption peaks, which decreased in proportion to the amount of platinum sites covered by bismuth. The catalytic activity of a series of Bi-MPtEs towards the oxidation of glucose was investigated by cyclic voltammetry, and the overall behaviour was found to be superior of that of the corresponding MPtEs. Also, at Bi-MPtEs, the effect of interference by ascorbic acid was minimal. Calibration plots were examined over the glucose concentration range from 0.5 mM to 300 mM. It was found that linearity, between current against glucose concentration, and sensitivity depended on the electrode type and real surface area. At the Bi-MPtEs both linear range and sensitivity were larger than those of the MPtEs. These results were discussed in terms of high tolerance of the Bi-MPtEs towards the intermediate poisons originated in the electrooxidation process of glucose.