A glassy carbon electrode was modified by co-immobilization of tyrosinase and a conducting poly( 1-vinylimidazo1e)-based osmium polymer on its surface. The ability of this biosensor to function as a detector for the HPLC determination of phenolic compounds, such as p-aminophenol, phenol, p-cresol, catechol and p-chlorophenol, was then assessed. The mobile phases investigated were binary mixtures of methanol and phosphate buffer. The effects of operational parameters, such as the concentrations of the electrode-modifying compounds, i.e., the osmium polymer and the cross-linking agent, poly(ethy1ene glycol), the mobile phase flow rate, the working potential and the biosensor's short-term stability were investigated and optimized. The biosensor exhibited a 100-200-fold improvement in sensitivity and detection limit when compared with a UV/VIS spectrophotometric detector. The amperometric phenol biosensor was able to detect catechol, phenol, p-cresol, m-cresol and four other phenolic compounds in cigarette filter tips.

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Four glucose sensors have been developed by modifying carbon paste electrodes with glucose oxidase as a biocomponent and a conducting redox osmium-polymer as the mediating compound. The enzyme was immobilized by crosslinking with glutaraldehyde and bovine serum albumin in three modifications of electrodes and physical adsorption in one electrode. The optimal concentrations of the modifying compounds were determined and the response of the sensors to 2-20 mM glucose were characterized. The influence of pH, temperature, interferences, and storage on the responses of the sensors were investigated.

Horseradish peroxidase (HRP) modified electrodes were constructed by entrapping the enzyme in an Eastman AQ 55D polymer. The biosensor detects butanone peroxide (BTP) as a substrate, and thiourea (THU) and ethylenethiourea (ETU) as HRP inhibitors. The kinetic parameters for this sensor in organic media such as I,,,,, and K for BTP detection and K for ETU and THU detection were evaluated. The differences in the values of these parameters were explained in terms of the physico-chemical properties of the organic reaction media. A possible solvent-induced deviation of ithe biosensor behavior from Michaelis-Menten kinetics in the detection of ETU and THU was evaluated using the Hill analysis. The least deviation was observed in acetonitrile. Spectroelectrochemistry was also used to qualitatively assess solvent-HRP, BTP-HRP and inhibitor-HRP interactions.