Metrolab Blog

PH Electrodes – Basic questions vol2

How to clean pH and ORP electrodes?

Find information in the operating manuals, the pH guide booklet and in the pH TroubleShooter on

In general:


  • Blockage of diaphragm with silver sulfide: use diaphragm cleaner containing thiourea (ME-51350102)
  • Blockage of diaphragm with silver chloride: soak the electrode in concentrated ammonia solution
  • Blockage of diaphragm with proteins: use electrode cleaner containing pepsin and HCl (ME-51350100)
  • Other junction blockages: clean electrode in ultrasonic bath or in 0.1 mol/L HCl solution


What is the normal lifetime of sensors?

When using and storing a pH electrode the usual way, the expected lifetime is 1 to 3 years. Some customers use their electrodes for up to 8 years! However there are a number of factors that can contribute to shortening the lifetime of an electrode. One of these is the use of hot and very alkaline samples. But even electrodes that have been well maintained and properly stored may start performing poorly after some time. In such cases it may be possible to regenerate the pH-sensitive glass membrane and restore the electrode to its previous level of performance using an ammonium bifluoride regeneration solution (ME-51350104). This regeneration solution is based on a highly diluted solution of hydrofluoric acid which etches away a very thin layer of the glass membrane, exposing a fresh surface area. The lifetime of electrodes with the SteadyForce reference system is mainly limited by the residual overpressure of the electrolyte. Depending on the requirements, it can used in the range of 6 to 12 months.

Conductivity probes do not age in the same way as pH electrodes. Their lifetime is not limited as long as their measuring poles are not attacked by any chemicals.