Time dependence of measured toxic effect

In common with enzyme based biosensors (equations (7.3) and (7.4)) the reduced mediator can be re-oxidized when it diffuses to an electrode poised at a suitably oxidising potential, e.g., 

An alternative approach, adopted by Albery et al. [59-61], is to determine the mechanism giving rise to the sensor response and to use this information together with the measured data at short times to calculate the final response. This was used for an electrochemical sensor system incorporating cytochrome oxidase where the steady-state responses of the measurement system were insufficiently fast for useful measurement of respiratory inhibitors such as cyanide, hydrogen sulphide, etc. By using mechanistic information, it was possible to successfully calculate the concentration in a test sample by real-time analysis of the sensor signals at short times after exposure to the test sample. The analysis could cope with the gradual loss of enzyme activity commonly found in these biosensor devices. 

Redox mediated whole cell biosensors for toxicity assessment 

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