Ion Selective Electrodes are electrochemical sensors which work on the principle of potentiometry which involves the measurement of the potential of a cell against a standard reference point, in this case, a simultaneous reading from a reference electrode.
ISEs are designed to respond to the presence of specific ions in the water and come in several types; solid state, gas sensors, liquid membrane and glass sensors. Proteus uses a mix of solid state and liquid membrane depending on the ion required.
While ISEs are generally considered ‘older’ technology, they remain unrivalled for water quality monitoring as they are easy to operate and relatively inexpensive. Whilst they have a shorter operational life than other sensors, there flexibility and ease of measurement ensure they remain an attractive choice throughout the water industry.
Solid state sensors are a little self-explanatory in that the sensor surface which comes into contact with the water is a ‘solid’ material usually consisting of single or a combination of ionic compounds. Which ionic compounds are used depend on that ion that sensor is designed to detect.
When the surface is submerged in water, the presence of the target ions in the water will create an ion exchange process leading to the formation of potential at the sensor surface.
These sensors have a thin membrane, Proteus uses sensors with a PVC based membrane. Within the membrane an ionophore or ion exchanger is embedded which will respond to the target ion for that sensor. This will allow the target ion to penetrate the membrane and take part in the reaction which will cause potential voltage to be generated.
• Chloride
• Ammonium
• Nitrate
• Sodium
• Calcium
• Bromide
Each Proteus equipped with one or more ISEs will have a separate reference electrode sensor included to enable measurement of Ions in water; electrical conductivity and pH/ORP sensors also use the reference electrode.
Some electrodes can be prone to interference in the presence of other ions. Please check at the time of purchase if you have any concerns.
