AB-083
Sodium analysis by ion-selective electrode
Summary
Measuring sodium using an ion-selective electrode (ISE) is an accurate, selective, and rapid analytical method. For the sodium measurement, the potential difference between the ion-selective electrode and a reference electrode is directly related to the sodium concentration in the sample solution, as described by the Nernst equation. Compared to chromatographic or spectroscopic methods, the ion-selective electrode method to determine sodium is inexpensive, space-saving, and easy to use.
This Application Bulletin describes how to measure the sodium ion concentration in different matrices with varying sodium levels such as table salt, drinking water, leachate, potato chips, and baby food (milk powder) using the separate sodium ion-selective electrode (also called Na-ISE) and a reference electrode. Both direct measurement with standard solutions and standard addition are demonstrated.
In the first section of this document, the principle of ion-selective electrodes for sodium is discussed. Additionally, some general tips are given for handling the electrode and the ion-selective membrane, about the ionic strength adjustment solution, and for the accurate measurement of sodium. The second part of the document presents practical examples to illustrate how to measure the concentration of sodium. These examples demonstrate the application of both direct measurement and the standard addition technique.