The pH electrode must be soaked before use, because pH bubble is a special glass membrane. There is a thin hydrated gel layer on the surface of the glass membrane. It can react well with H+ ions in the solution only under full wetting conditions. At the same time, the dissymmetrical electric potential can be greatly reduced and tend to be stable when the glass electrode is soaked. PH glass electrodes can usually be soaked in distilled water or pH4 buffer solution. It is usually better to use pH4 buffer solution for 8 hours to 24 hours or longer, depending on the thickness of the glass film and the aging degree of the electrode. At the same time, the reference electrode of liquid junction also need to soak. Because if the liquid junction dry will make the liquid junction potential is increased or unstable, the reference electrode must be soaking liquid and the reference electrode of the reference solution, generally a few hours soaking time.

Therefore, the pH composite electrode, it must be soaked in pH4 buffer with KCl, so as to play a role in the glass bulb and liquid. It must be noted that because in the past people using pH single glass electrode has been in the habit of using deionized water or pH4 buffer for, still using the immersion method that later using pH composite electrode, even in some incorrect pH composite electrode used in the specification will be the wrong guide. A direct consequence of this error caused by immersion method is to make a good performance of the pH composite electrode electrode into a slow response, poor accuracy, and immersion time performance worse, because after a long time of soaking, the internal liquid junction (e.g. sand core internal) KCl concentration has been greatly reduced, so that the the liquid junction potential increases and instability. Of course, the electrode will recover as long as it is soaked in the correct soaking solution for several hours.

In addition, the pH electrode can not be soaked in neutral or alkaline buffer solution, and the long-term immersion in such solutions will cause the response of the pH glass film to be slow.

Correct preparation of pH electrode immersion solution: take a package of pH4.00 buffer (250ml), dissolve in 250ml pure water, add 56 grams of pure KCl, heat it properly, stir until completely dissolved.

In order to make the pH composite electrode is more convenient to use, some of the imported pH composite electrode and the electrode in the domestic part, pH composite electrode head is equipped with a sealed plastic bottle, filled with the electrode solution, the electrode head long soak the use of pull out the wash can be very convenient. This preservation method is not only convenient, but also beneficial for prolonging the life of electrodes. However, the soaking solution in plastic bottles should not be polluted, so we should pay attention to the replacement.