Thermodynamic Origin Of The Sub-Nernstian Response Of Glass Electrodes

A thermodynamic explanation of the sub-Nerstian response of pH glas electrodes is presented on the basis of the dissociation mechanism, which attributes the functioning of glass electrodes to the phase boundary equilibrium of functional groups at the glass surface and ions in the solution. It is found that the activity change of the functional surface groups caused by pH variations, which basically reduces the electrode slope, cannot be neglected and results in a measurable electromotive efficiency below 1.