How to properly soak the pH combination electrode of the portable analyzer?

The pH electrode must be soaked before use, because the pH bulb is a special glass membrane, and there is a very thin hydrated gel layer on the surface of the glass membrane, which can have a good interaction with the H+ ions in the solution only under fully wet conditions. response. At the same time, the glass electrode is soaked, which can greatly reduce the asymmetric potential and tend to be stable. The pH glass electrode can generally be soaked in distilled water or pH4 buffer solution. Usually it is better to use pH4 buffer solution, and the soaking time is 8 hours to 24 hours or longer, depending on the thickness of the bulb glass membrane and the aging degree of the electrode. At the same time, the liquid junction of the reference electrode also needs to be soaked. Because if the liquid junction dries up, the potential of the liquid junction will increase or become unstable. The soaking solution of the reference electrode must be consistent with the external reference solution of the reference electrode, and the soaking time is generally a few hours. Therefore, for the pH composite electrode, it must be immersed in the pH4 buffer solution containing KCl, so that it can act on the glass bulb and the liquid junction at the same time. Special attention should be paid here, because in the past, people used to use a single pH glass electrode and were used to soaking it in deionized water or pH4 buffer solution. Later, they still used this soaking method when using a pH composite electrode, even in some incorrect pH composite electrodes. This kind of erroneous guidance is also carried out in the instruction manual of the electrode. The direct consequence caused by this wrong soaking method is to turn a pH composite electrode with good performance into an electrode with slow response and poor precision, and the longer the soaking time, the worse the performance, because after a long time soaking, the liquid junction The concentration of KCl inside the boundary (such as inside the sand core) has been greatly reduced, which increases and stabilizes the potential of the liquid junction. Of course, the electrodes will recover with just a few hours of re-soaking in the correct soaking solution. In addition, the pH electrode should not be soaked in neutral or alkaline buffer solutions. Long-term immersion in such solutions will cause the pH glass membrane to respond sluggishly.