When using the pH meter, is there a maximum amount of time the electrode can be absorbed in the solution?
The pH meter/acidity meter electrode must be soaked before use, because the bulb of the pH meter/acidity meter is a special glass membrane, and there is a very thin hydrated gel layer on the surface of the glass membrane, which can only be compatible with the pH meter under fully wet conditions. The H+ ions in the solution have a good response. At the same time, the asymmetric potential can be greatly reduced and stabilized after soaking the glass electrode. Generally, the glass electrode of the pH meter/acidity meter can be soaked in distilled water or pH meter/acidity meter 4 buffer solution. Usually it is better to use pH meter/acidity meter 4 buffer solution, the soaking time is 8 hours to 24 hours or longer, depending on the thickness of the bulb glass film 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 immersion solution of the reference electrode must be consistent with the external reference solution of the reference electrode, that is, 3.3mol/L KCL solution or saturated KCL solution. The time is generally a few hours. Therefore, for the pH meter/acidity meter composite electrode, it must be soaked in the pH meter/acidity meter 4 buffer solution containing KCL, so that it can work on the glass bulb and the liquid junction at the same time. Special attention should be paid here, because in the past people used a single pH meter/acidity meter glass electrode and were used to soaking it in deionized water or pH meter/acidity meter 4 buffer solution, and later when using a pH meter/acidity meter composite electrode Using such a soaking method, even in the instruction manual of some incorrect pH meter/acidity meter composite electrodes, this kind of wrong guidance will be carried out. The direct consequence of this wrong soaking method is to make a pH meter with good performance The composite electrode of the pH meter/pH meter becomes an electrode with slow response and poor precision, and the longer the immersion time, the worse the performance, because after a long time of immersion, the KCL concentration inside the liquid junction (such as inside the sand core) has been greatly reduced , making the liquid junction potential increased and unstable. Of course, as long as it is re-immersed in the correct soaking solution for several hours, the electrode will still recover.
In addition, the pH meter/acidity meter electrode should not be soaked in neutral or alkaline buffer solutions. Long-term immersion in such solutions will cause the glass membrane of the pH meter/acidity meter to respond slowly. Correct pH meter/acidity meter electrode immersion Solution preparation: Take a pack of pH meter/acidity meter 4.00 buffer (250ml), dissolve it in 250ml pure water, add 56 grams of analytical pure KCl, heat properly, and stir until completely dissolved. There are bottled electrodes on the market The soaking solution is supplied in two sizes: 500ml and 50ml. These soaking solutions contain preservative ingredients, will not mold and deteriorate, and have a shelf life of one year.
In order to make the pH meter/acidity meter composite electrode more convenient to use, some imported pH meter/acidity meter composite electrodes and some domestic electrodes are equipped with a sealed plastic vial at the head of the pH meter/acidity meter composite electrode, and the electrode inside is soaked. The electrode head is soaked in it for a long time, and it is very convenient to pull out and wash it when using it. This storage method is not only convenient, but also very beneficial to prolong the life of the electrode, but the soaking solution in the plastic vial should not be polluted. replace.
