Combination pH electrode with stable standard potential

A combination glass pH electrode, the standard potential of which is stabilized by means one or more of the following structural modifications:

• (a) incorporation of a noble metal internal element in the pH half-cell, said noble metal by reason of its inertness maintaining its purity of composition and not degrading the purity of composition of solutions in contact with it;
• (b) incorporation of a noble metal internal element in the reference half-cell as in the pH half-cell, said noble metal by reason of its inertness maintaining its purity of composition and not degrading the purity of composition of solutions in contact with it;
• (c) incorporation of an internal pH bulb electrolyte with stable pH and oxidation-reduction potential, said electrolyte by reason of its stable pH maintaining a stable interfacial potential at a pH-sensitive glass surface and by reason of its stable oxidation-reduction potential maintaining a stable electrochemical potential in contact with a noble metal;
• (d) incorporation of an homogenous reference electrolyte with stable oxidation-reduction potential and equitransferent salt, said electrolyte by reason of its stable oxidation-reduction potential maintaining a stable electrochemical potential in contact with a noble metal and by means of its equitransference maintaining a low and stable junction potential in contact with an electrolyte of differing composition;
• (e) incorporation of a liquid junction composed of a porous, inert material;
• (f) incorporation of a reference electrolyte compartment vent that minimizes moisture loss or pick-up from the surroundings yet admits sufficient air to permit flow of reference electrolyte through the liquid junction under the influence of gravity;
• (g) incorporation of a storage sleeve into which the glass bulb, liquid junction, and vent portions of the electrode can be sealed such that moisture loss is eliminated during storage;
• and/or
• (h) incorporation of an absorbent medium located in the storage sleeve and in contact with the glass pH bulb such that said absorbent medium, when intentionally moistened with water or when becoming moistened due to reference electrolyte leaking from the electrode's liquid junction, serves to maintain high humidity in the interior of the storage sleeve and further serves to maintain the pH bulb in a hydrated state.