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 or even may be chemically reacted with the electrolyte or the inner electrode (for example, AgCl Sulfide → Ag2S) and the electrode is poisoned.

In the strong oxidising medium, the loss of alkaline substances (mainly monovalent cations) in the sensitive glass membrane, which damages the hydration layer, can cause poisoning of the ph meter electrode. Acid ph meter electrode can be selected, its manufacturing process using special process measures (special addition of ionic formulations), 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 H3 O, so that the ph meter electrode surface of the H number of relative reduction in the ph value increases. In strong alkali media Na will also participate in the solution of H and electrode hydration layer on the H exchange process, resulting in ph meter electrode potential increases ph value is low.