The systematic study of the effect of binder viscosity on the sensitivity of a tyrosinase-based carbon paste electrode (CPE) biosensor for phenol and catechol is reported. Silicon oil binders with similar (polydimethylsiloxane) chemical composition were used to represent a wide range of viscosities (10-60 000 mPa s-1 at 25°C) while minimizing polarity effects. The highest response for both phenol and catechol was achieved using a silicon oil binder of intermediate viscosity (100 mPa s-1). The binder viscosity showed no appreciable effect on the direct oxidation of phenol and catechol using a plain CPE, suggesting the involvement of diffusion kinetics in the binder matrix for the enzyme-based CPE. The effect of the relative binder concentration in the carbon paste was measured over the range of 30-70%. Optimal results were obtained using 40% silicon oil. For comparison of the viscosity effects observed with the carbon paste electrode (CPE) containing silicon oil, other low and high viscosity mineral oils and paraffin waxes were also examined.
- Carbon paste electrode