Types of Ion Selective Membrane
You can find four primary types of ion selective membrane employed in ion selective electrodes: solid state, glass, compound electrode and liquid based.
Crystalline membranes are produced from mono- or polycrystallites of an individual substance.
Glass membranes are created from an ion-exchange kind of glass (silicate or chalcogenide).
These electrodes are made from glass capillary tubing around 2 millimeters in diameter, a sizable batch at a time.
Ion-exchange resin membranes
Ion-exchange resins are according to special organic polymer membranes which have a specific ion-exchange substance (resin).
Fluoride ion selective electrode is a kind of ion selective electrode sensitive for the concentration of the fluoride ion. A typical example is the lanthanum fluoride electrode.
Within the lanthanum fluoride electrode, the sensing component is a crystal of lanthanum fluoride LaF3, doped with europium fluoride EuF2 to produce lattice vacancies. This type of crystal is an ionic conductor through virtue of the mobility of fluoride ions that jump between lattice vacancies.
An electrochemical cell might be constructed utilizing such a crystal like a membrane separating 2 fluoride solutions. This cell works as a concentration cell with transference in which the fluoride transport number is 1.
As transference of charge via the crystal is nearly exclusively because of fluoride, the electrode is extremely specific to fluoride.
The cell diagram of a standard experimental arrangement is:
Cu' | Ag,AgCl | KCl || solution | LaF3 | KF,KCl | AgCl,Ag | Cu
Cu' | Ag, AgCl | KCl is an exterior reference electrode
KF,KCl/AgCl,Ag/Cu is an inner reference in the fluoride selective electrode
Calcium Ion Selective Electrode is utilized to simply, quickly, accurately and economically calculate calcium concentration within aqueous solutions.
The Calcium Ion Selective Electrode contains an electrode body made up of an ion exchanger within a sensing module. This sensing module includes a liquid inner filling solution in touch with a gelled organophilic membrane made up of a calcium ion selective exchanger.
An electrode potential grows around the membrane. Once the membrane is in touch with a calcium solution. Measurement of the potential against a continuing reference potential, making use of an ISE Amplifier and Science Workshop interface, depends upon the level of free calcium ion in solution. The stage of calcium ions, related to the measured potential, is explained by the Nernst equation:
E = Eo + S log X