Sensitivity of potentiometric sensors based on Nafion®-type membranes and effect of the membranes mechanical, thermal, and hydrothermal treatments on the on their properties

Abstract

The effect of heat treatment and mechanical deformation at different relative humidity on the transport properties of ion exchange Nafion® type membranes and characteristics of the potentiometric sensors based on them were studied. Methods for treatment of ion-exchange Nafion® type membranes were proposed for obtaining materials with given properties, including materials with improved selectivity of cation transport. An explanation for the changes in the pore and channel system during membrane treatment was proposed. A correlation between water uptake, transport properties of Nafion® type membranes and sensitivity of potentiometric sensors based on Donnan potential (DP) to amino acid and hydroxonium ions was revealed. Thermal treatment of membranes at RH<100% results in higher determination accuracy of amino acid ions due to decreasing off of the sensor sensitivity to interfering hydroxonium ions. The best value of DP-sensor sensitivity to amino acids ions was 51±2mV/pC in a concentration range 1.0·10−4–1.0·10−1M. The detection limit reached 7·10−6M. The relative error for amino acid determination in the pH range from 3 to 5 was 0.9–10%, the response time and drift of sensor did not exceed 1min and 7mV/h respectively. Presumably, targeted changes in the membrane properties due to their treatment will improve the parameters of processes and devices based on ion-exchange membranes.