CHAPTER 4 - Analytical Techniques using Membrane Electrodes

Abstract

Publisher Summary This chapter discusses the use of membrane electrodes in analytical applications. For analytical applications, ion-selective electrodes have to be calibrated. Unlike pH-sensitive glass electrodes, a very limited number of ion-buffers are available for the calibration of ion-selective electrodes. In general, the calibration of ion-selective electrodes ought to be carried out under similar conditions as those for sample measurements. For this purpose, suitable standard materials and an appropriate calibration method should be chosen. It is a common practice to standardize ion-selective electrodes using serially diluted solutions of a completely dissociated salt of the ion of interest, but the results can become irreproducible at concentrations below 10 –4 –10 –5 M. The need for generally valid activity-potential scales for the calibration of the ion-selective electrodes, consistent among themselves and with the generally accepted pH convention, appears to be necessary. Direct potentiometry is the simplest method of all in the use of ion-selective electrodes. After preparing a calibration curve with two or three standard activities or concentrations, the ion-selective membrane electrode and reference electrode can be placed in the sample solution and the measurements are made in much the same way as pH measurements.