MICRO ENZYME-SENSOR WITH AN OSMIUM COMPLEX AND POROUS CARBON FOR MEASURING GALACTOSE

Citation
K. Miyata et al., MICRO ENZYME-SENSOR WITH AN OSMIUM COMPLEX AND POROUS CARBON FOR MEASURING GALACTOSE, Bulletin of the Chemical Society of Japan, 68(7), 1995, pp. 1921-1927
Citations number
47
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Chemistry
ISSN journal
0009-2673
Volume
68
Issue
7
Year of publication
1995
Pages
1921 - 1927
Database
ISI
SICI code
0009-2673(1995)68:7<1921:MEWAOC>2.0.ZU;2-E
Abstract
A micro enzyme-sensor, based on galactose oxidase (EC 1.2.3.9) and a t ris(2,2'-bipyridine) complex of osmium(II/III) as a redox mediator ([O s(bpy)(3)](2+)/(3+)), fabricated on a carbon electrode (25 mu m diamet er), was developed for measuring galactose. To obtain the carbon elect rode, a platinum-disk electrode (25 mu m diameter) was etched in hot a qua regia to create a cavity (depth of ca. 3-5 mu m) at its tip. A por ous carbon material was prepared from 90% acetylene black and 10% Tefl on emulsion as a binder, and then packed into the cavity of the platin um-disk electrode's tip. The carbon electrode was immersed in the osmi um complex with 0.1 mol dm-3 LiClO4 in order to adsorb it in the carbo n pores, which was monitored based on an increase in the anodic peak c urrent and the cathodic peak current based on the osmium complex redox potential by the cyclic voltammogram. The tip of the carbon electrode was dipped overnight in a buffer solution of pH 7.00 containing galac tose oxidase so as to immobilize it on this surface by adsorption. The characteristics of the porous-carbon material surface by X-ray diffra ction (XRD) and scanning electron microscopy (SEM), the calibration cu rve for measuring of galactose, and the effects of the pH, temperature and concomitant compounds were investigated. By the XRD measurement, the porous carbon after treating a Zonyl FSN fluoro-carbon surfactant solution, a 5% NafionR solution with methanol, and an osmium complex w ith 0.1 mol dm-3 LiClO4 showed good crystallinity compared with carbon powder. The structure of the carbon-electrode surface was visually co nfirmed using SEM photographs. The carbon surface had many pores, and galactose oxidase existed on it after adsorption. Under the optimum co nditions the amperometric response of this sensor was linear over conc entration ranges of 0.01-5.00 mmol dm(-3) galactose; the correlation c oefficient was 0.999.