Theoretical predictions on the response properties of potentiometric gas sensors based on internal polymer membrane electrodes

Abstract

The appropriate equilibrium expressions and known thermodynamic equilibrium constants are used in calculations on the expected response properties of polymer membrane electrode-based ammonia and carbon dioxide gas sensors. Slopes, detection limits, Nernstian response ranges and selectivities of such devices are shown to be a function of the initial pH, ionic strength and equilibrium constant of the internal electrolyte buffer used within these probes. Previously reported data for an ammonia sensor of this type correlate well with the theory. The poor response characteristics of carbon dioxide sensors based on internal carbonate-responsive membranes is also explained via the model presented. Future prospects and considerations for the development of other gas sensors of this type are discussed.