PRELIMINARY INVESTIGATION OF A BIOELECTROCHEMICAL SENSOR FOR THE DETECTION OF PHENOL VAPORS

This work investigates the feasibility of constructing a bioelectroche mical sensor that can operate directly in gases. A series of experimen ts are described, resulting in a sensor that is responsive to phenol v apours. The sensor was based on ionically conducting films that incorp orate a biological redox catalyst at the surface of an array of interd igitated microband electrodes. Exposure to phenol vapour drives the bi oelectrochemical reaction, providing a basis for a current signal unde r constant potential conditions. Ionic materials included Nafion and f ilms based on tetrabutylammonium toluene-4-sulphonate (TEATS). The qua si-reversible electrode reaction of potassium hexacyanoferrate (II) wi thin TEATS was investigated as a function of drying time. E(0)' and k( 0) were determined at a TEATS modified microdisc electrode under stead y-state conditions. Drying time (water loss) from the TEATS film had t he effect of increasing the film ionic strength. It was shown that as the film ionic strength increased, E(0)' for potassium hexacyanoferrat e (II) shifts toward positive potentials (because of ion pairing) and there was a corresponding increase in the heterogeneous rate constant, k(0). The latter effect was attributed to increasing ion-ion (cation- ferrocyanide ion) interactions as the film dried and the enhancing eff ect this had on the prevention of surface poisoning reactions at the e lectrode. These factors are discussed in relation to sensor design.