Isolation and identification of drift sources in planar ion sensors during initial water uptake: correlation of model and experiment

A method to isolate and measure the membrane potential drift arising from a gradient in water concentration across an ion-selective membrane is presented. Calculations based on the dual-sorption site model for water uptake show the time constant of the initial potential drift, starting from an asymmetric water distribution, is identical to the time constant for equilibration of mobile water concentration within a membrane. Factors such as total salt content, and ratio of poly(vinylchloride) to plasticizer content were found to affect the equilibration rate, with less plasticizer giving faster equilibration