Subsurface concentration profiling by Ion Bombardment for Spectrochemical Analysis (IBSCA) and Nuclear Reaction Analysis (NRA) combined with other methods yielded information on the ionic processes at and in glass electrode membranes and results in the mechanism (dissociation mechanism) of glass electrodes. The primary step is the formation of a phase boundary equilibrium between functional groups, e.g. siloxy, at the glass surface and hydronium or alkali ions in the solution. It determines the potential of the glass due to the charge density established at the glass surface by the dissociated form of the surface groups, e.g. =Si0-, and the surface activities of the acidic or salt forms of the surface groups, e.g. =SiOH and =Si0M, respectively.
