One-dimensional modelling of foulant reduction in a microflow, amperometric-sensor system

This paper presents one-dimensional simulations of an experimental, amperometric sensor system designed to reduce fouling at the sensor surface. The effect exploited in this system depends on differences in the diffusion coefficients of the analytes and foulants. We describe this effect and present simulations of a typical analyte (H2O2) and foulant (bovine serum albumin). The simulations show effective reduction of foulants: the concentration at the sensor surface is more than five orders of magnitude smaller than in the sample, while concentration of analyte is only reduced by one order of magnitude, and so remains measurable. Thus in cases where the target species has a lower diffusivity than the foulant (for example ions in samples containing protein) this technique can be very effective in extending the maintenance interval or lifetime of a sensor and increasing its operational value. Using a calibration factor obtained from experiments to relate concentration to amperometric signal, we predict a signal strength from the simulations that is consistent with the experimental results. The peak signal is approximately 10(-7) Amps in both simulation and experiment, and the time taken to reach this peak value is within a factor of three.