Ion selective electrodes, also known as ion electrodes, are electrodes that react to specific ions in an aqueous solution. Although a pH-sensitive glass electrode can be considered as a hydrogen ion electrode, it is generally not considered as an ion electrode.
Ion electrodes have been studied since the 1960s and HORIBA has developed and sold many kinds of ion electrodes from early on.
To determine the ion concentration of a specific ion, an ion meter (or a pH meter capable of measuring ions), is connected to the relevant specific ion electrode and a reference electrode. These are then dipped in a test solution. By measuring the electromotive force between the two electrodes, the specific ion concentration in the test solution is obtained.
To determine the calibration curve, or compensate for sensitivity, two types of reference solutions with different concentrations of the specific ion are required. The sensitivity of ion electrodes is affected by temperature variations, so measurement must be performed at a constant temperature.
The selectivity coefficient is a measure of how much the ion electrode responds to other ions that have properties similar to the ion of interest.
Response Membranes for Ion Electrodes
Response membranes for ion electrodes include glass membranes (for Na+ electrodes), silver-salt based solid state membranes (for the corresponding CN-, Cl-, S2-, I-, Br-, SCN-, Cu2+, Cd2+, Pb2+, or Ag+ electrode), single crystal membranes (for F- electrodes), liquid membranes and plastic solidification membranes (for No3-, K+, Na+, and Ca2+ electrodes), and diaphragm (for ammonia electrodes).
This information has been sourced, reviewed and adapted from materials provided by HORIBA Scientific.
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