How to prolong the service life of pH meter electrodes?
1. Electrode Composition
To understand electrode life, it is first necessary to understand the composition of the electrode.
The pH meter used in the textile laboratory generally uses a pH composite electrode. Its structure is mainly composed of an electrode bulb, an electrode shell, a reference electrode, a reference solution, a junction, an electrode cap, an electrode wire, and a socket. Electrode bulb: It is made of molten lithium glass with hydrogen function and is spherical in shape, with a film thickness of about 0.1-0.2mm and a resistance value of <250 megohms (25°C).
Note: Please refer to the instruction manual for specific model composition.
2. Factors affecting electrode life
Generally, when asked about the life of electrodes, many experts and teachers, including manufacturers, will say that it is one year, which is not accurate. In addition to electrode quality and production date, electrode life is determined by other factors.
1. First, the sample solution to be tested
For example, in the textile industry, the same electrode is in contact with different test solutions. Some test solutions are single and non-polluting. For example, in general textiles, some test solutions have strong acid and alkali or fluffy and oily solutions. Shorten the service life of the pH electrode. For example, the normal test pH meter can be used for one year, but the frequent test of strong acid and strong alkali pH meter may not work for half a year.
2. The second is the use of time
Long-term non-use or high-frequency use will affect the life of the electrode. For example, some laboratories use it once a day, sometimes even for a few days, and some use it non-stop every day. Then the pH meter that is frequently used every day or that is not frequently used may have a short life. Reasonable use of the pH electrode that is not idle is the best way to extend the life.
3. The third is whether you choose the wrong model
If the electrode is found to be inaccurate within a few days of use, it may be that the electrode model is selected incorrectly or the user has improperly used it. Even if the frequency of use is very low, the supplier is not responsible for the return or replacement of the product in this case.
Another situation is that the pH electrode is broken shortly after use or the test is inaccurate, the data is unstable, and the electrode is often used, the appearance is well maintained, and the usual maintenance is strictly in accordance with the instructions, then it may be the electrode. For quality problems, the supplier should be responsible for the return.
The general use time of an electrode is half a year to one year, and the time of industrial pH electrodes with poor use conditions may be shorter.
3. Appropriate operation can protect the pH electrode
1. Correct selection of pH buffer solution
A pH buffer solution is a solution that maintains a stable pH under normal conditions. Even if a small amount of acid or alkali is added to this solution, the pH value of this solution is basically constant. This kind of solution that can resist a small amount of acid-base interference and keep the pH value constant is called a pH buffer solution.
⑴The pH meter must be calibrated at least once a day before use. For example, if you use the buffer solutions commonly used in national standard textiles, pH4.00, pH6.86, and pH9.18, you can use one-point calibration, two-point calibration, and three-point calibration. Generally, pH meters have options , under normal circumstances, there are at least several standard buffer solution groups from China, Japan, and the United States or the component options of 1, 2, and 3
(2) It is generally used to calibrate or verify the pH meter, such as the buffer solution pH4.00 and pH6.86 commonly used in national standard textiles. After calibrating the pH meter, insert the pH electrode into the buffer solution of pH9.18 and pH4.00 to verify the pH Whether the display value of the meter is the same as the pH value of the standard solution
2. When not in use, the pH electrode soaking method
The pH electrode should be soaked before use. The pH bulb is a special glass membrane with a thin hydrated gel layer on the surface of the glass membrane. It can only respond well to the H+ ions in the solution under the condition of sufficient humidity. . At the same time, the glass electrode is soaked, which can greatly reduce the asymmetric potential and tend to be stable. Usually use 3.3mol/L KCL solution, the soaking time is generally more than 12 hours, but avoid crystallization of 3.3mol/L KCL solution, the crystallization can be washed off with distilled water, and cannot be scraped off with other tools, etc.
3. Precautions for using the composite electrode of the pH meter
① Check the electrode bulb before the test. There should be no air bubbles at the front of the bulb. If there are air bubbles, shake them off with a little force.
② After the electrode is taken out of the soaking solution, it can be cleaned in the third-grade water, and the bulb must not be wiped with a paper towel, otherwise, due to the electrostatic induction charge transfer to the glass film, the time for potential stabilization will be prolonged, and the measured solution can also be used directly Rinse the electrode.
③The pH compound electrode is inserted into the solution to be tested at least 1CM below. Before the test, stir it several times and then place it statically. This will speed up the response speed of the electrode and stabilize the test value.
