Causes of pH meter electrode poisoning
Flow type reference pH meter electrode, the formation of electrical channels depends on the micro-osmotic pressure of the electrolyte in the electrode, so that the electrolyte penetrates into the measurement solution. When the medium pressure or concentration is high, the fluid replacement channel is not smooth, or there are air bubbles, etc., it may hinder the leakage of the electrolyte and increase the intermediate impedance of the electrical path. If the medium reverses into the electrode of the pH meter, it will pollute the salt bridge or even It may cause chemical reaction with electrolyte or internal electrode (eg AgCl sulfide→Ag2S) to poison the electrode.
In a strong oxidizing medium, the loss of alkaline substances (mainly monovalent cations) in the sensitive glass membrane will damage the hydration layer and cause poisoning of the electrode of the pH meter. The acid-resistant ph meter electrode can be selected, and the special process measures (specially added ion formula) adopted in the manufacturing process have enhanced the anti-acidosis ability of the glass membrane, and at the same time, the zero potential of the electrode corresponds to pH0=2, so that the pH in the acid range Linearity is corrected.
The pH meter electrode does not have a good linear relationship outside of pH2~pH9, and a large amount of hydronium ion H3O is easily formed in a strongly acidic solution, so that the number of H on the surface of the pH meter electrode decreases relatively and the pH value increases. Na in the strong alkaline medium will also participate in the exchange process between the H in the solution and the H on the electrode hydration layer, resulting in an increase in the electrode potential of the pH meter and a low pH value.
