MEMBRANE-FREE, RHODIUM-MODIFIED, METHYL SILICATE-GRAPHITE AMPEROMETRIC BIOSENSOR

A rhodium-modified amperometric biosensor based on the recently introd uced ceramic-carbon composite electrode has been developed. The sensor s are comprised of Rh metal and glucose-oxidase-modified graphite part icles embedded in a porous, organically modified silicate network. The hydrophobicity of the matrix imparts limited wettability. The thickne ss of the active layer of the electrode can be tuned by incorporating hydrophilic components such as metal particles and proteins. This laye r can be removed by mechanical polishing to reveal a fresh uncontamina ted reactive layer. In the present construction, rhodium is used for e lectroreduction of the biochemical reaction product, hydrogen peroxide . The continuous supply of oxygen from the top of the electrode throug h the porous structure facilitates operation even in oxygen-free solut ions, in a gas diffusion/biosensing mode of operation. Operation in cl inical blood plasma shows that the electrode can be used conveniently for analysis of biological samples. The sensor can be used at very low overpotentials and is free of common interferences, such as ascorbic acid, acetaminophen, uric acid, urea and salicylic acid. It is found t o be stable over long periods. (C) 1997 Elsevier Science S.A.