Advanced Topic 602 of 1102 Acids, Bases & Electrochemistry
Ion-Selective Electrodes
Sensors such as the glass pH electrode that respond to a specific ion.
Practise Acids, Bases & Electrochemistry All Acids, Bases & Electrochemistry topics
In-depth explanation of Ion-Selective Electrodes
An ion-selective electrode has a membrane that responds selectively to one ion, producing a potential that varies with the logarithm of the activity of that ion. The glass electrode, which responds to hydrogen ions, is the most widely used example, and fluoride and potassium electrodes are also common. The membrane allows only the target ion to exchange across its surface, so the potential is largely independent of other ions present. These electrodes give rapid and inexpensive measurements in clinical, environmental and industrial analysis. Their selectivity is described by a selectivity coefficient.
Going deeper: Ion-Selective Electrodes
Key ideas: An ISE responds to one ion through a selective membrane: glass for H+ and Na+, LaF3 crystal for F-, valinomycin liquid membrane for K+. Potential follows E = const + (0.0592/z) log a(ion) at 25 C, so a tenfold change in activity gives about 59 mV for z = 1. Calibrate with standards, and add TISAB to fix ionic strength.
Common mistakes and connections: Mistakes: reading the electrode as concentration rather than activity, ignoring interfering ions (selectivity coefficients), and neglecting temperature or drift. Response is logarithmic, so errors in mV correspond to about 4 percent error per mV in concentration for monovalent ions. Used in clinical analysers, water testing and the pH electrode.
Visualization of Ion-Selective Electrodes
An ion-selective electrode obeys the Nernst equation, with a response of about 29.6 mV per tenfold activity change for a 2+ ion such as Ca2+. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Blood analyzers use ion-selective electrodes to measure potassium and sodium concentrations quickly.
Frequently asked questions about Ion-Selective Electrodes
What is Ion-Selective Electrodes?
Sensors such as the glass pH electrode that respond to a specific ion.
Is Ion-Selective Electrodes a beginner, intermediate or advanced topic?
Ion-Selective Electrodes is a advanced topic in Acids, Bases & Electrochemistry. It builds on beginner and intermediate topics, so review those first if needed.
What should I learn before Ion-Selective Electrodes?
Study these earlier topics in Acids, Bases & Electrochemistry first: Overpotential, Pourbaix Diagram, Latimer and Frost Diagrams.
What comes after Ion-Selective Electrodes?
The next topics in Acids, Bases & Electrochemistry are pH Meter and Hydrogen Production by Electrolysis.
Can I practise Ion-Selective Electrodes with quizzes?
Yes. The interactive lesson includes a self-check question on Ion-Selective Electrodes, and the Acids, Bases & Electrochemistry quiz draws on every topic in this area.
Where Ion-Selective Electrodes fits in Acids, Bases & Electrochemistry
Ion-Selective Electrodes is topic 92 of 105 in Acids, Bases & Electrochemistry.