Polymer Membrane Electrodes
Consist of various ion exchange materials in an inert matrix such as PVC, polyethylene or silicone rubber. The membrane is sealed to the end of a PVC tube. The potential developed at the membrane surface is related to the concentration of the species of interest. Electrodes of this type include Potassium, Calcium and Nitrate.

Solid State Electrodes
Utilize relatively insoluble inorganic salts in a membrane. Solid state electrodes exist in a homogeneous or heterogeneous forms. In both types potentials are developed at the membrane surface due to the ion exchange process. Examples of this type of electrode include silver / sulfide, chloride and fluoride.

Gas Sensing Electrodes
Gas sensing electrodes are available for the measurement of ammonia, carbon dioxide, and nitrogen oxide. This type of electrode has a  gas permeable membrane and an internal buffer solution. The pH of the buffer solution changes as the gas reacts with it. The change is detected by a combination pH sensor within the housing. This type of electrode does not require a an external reference electrode.

Glass Membrane Electrodes
Glass membrane electrodes are formed by the doping of the silicon dioxide glass matrix with various chemicals. The most common of the electrode of this type is the pH electrode. Glass membrane electrodes are also used for sodium ions.