Solid State Membrane Electrodes:

In solid state membrane electrode we use a doped single crystal membrane in place of glass membrane. Those modifications enable us to design electrodes which have a response to a number of different anions and cations such as F^- , Cl^- , and Ag^- . A typical design is shown in Figure.

In this electrode system similar to glass electrode internal solution and electrode form the internal reference.  For instance, fluoride ion chosen electrode consists of LaF₃ membrane and an internal AgCl, Ag, reference electrode immersed within an internal solution of KF, KCl. The LaF₃ membrane is highly selective and responds to fluoride ion only. If this electrode used with reference saturated calomel electrode, the complete cell may be written as:

Hg,Hg₂Cl₂ (s) |  KCl ||   F^- (unknown)   LaF₃(s) |   NaF(0.1 M) |   NaCl (0.1M)|   AgCl (s), Ag

Figure: A typical solid state electrode