What are the reasons why the electrodes of a pH meter are easily damaged?
Many people, encountered such a problem, their own field use of the pH meter, use not long period of time, there will be electrode damage, not at all and the manufacturer said, the use of time so long, is it a manufacturer of electrodes have problems? If you try to change the electrodes of other manufacturers, this situation may also occur, what is going on? After careful consultation, you will find that the medium you measure leads to electrode poisoning.
The electrode produced on the market now is a flow-type reference pH meter electrode, the formation of the electrical channel relies on the electrolyte within the electrode micro-osmotic pressure, so that the electrolyte penetrates into the measurement solution. When the medium pressure or concentration is high and the replenishment channel is not smooth, or the presence of air bubbles and other circumstances, may hinder the electrolyte exudate, increasing the middle impedance of the electrical pathway, if the medium back seepage into the ph meter electrode, the contamination of the salt bridge may even be chemically reacted with the electrolyte or the inner electrode (for example, AgCl sulphide → Ag2S) and make the electrode poisoned.
In the strong oxidative medium, sensitive glass membrane in alkaline substances (mainly monovalent cations) loss, so that the hydration layer is damaged, will cause ph meter electrode poisoning. Acid-resistant pH meter electrodes can be used, the manufacturing process of special process measures (special additive ion formula), enhanced glass membrane acid poisoning resistance, while its electrode zero potential corresponds to pH0 = 2, so that the acidic range of linearity is corrected.
pH meter electrode in pH2 ~ pH9 outside does not have a good linear relationship, in a strong acidic solution is easy to form a large number of hydrated hydrogen ions H3O, so that the ph meter electrode surface of the number of H is relatively reduced ph value increases. Na in strong alkaline media will also participate in the solution of H and electrode hydration layer on the exchange process of H, resulting in ph meter electrode potential increases ph value is low.
