Numerical analysis of a theoretical one-dimensional amperometric enzyme sensor

The switch-on transient in a miniaturised amperometric sensor with an enzyme layer covered by a diffusion retardation layer is analysed theoretically. The time-dependent mass transfer equations with enzyme catalysed reactions are solved numerically in a one-dimensional geometry with a stationary liquid sample of the same size as the active sensor volume. No steady-state operation is normally achieved and the sensor structure and material parameters have a complicated effect on the oxygen flow behaviour. The theoretical model is used to calculate the measuring range, sensitivity and response time of the sensor. Their dependence on sensor structure is presented in a dimensionless form suitable for sensor design and for analysis of measurement data.