Common problems in the use of pH meter
1. How to judge whether the pH composite electrode is normal
In the calibrated state, the response is slow, and the inability to stabilize is a manifestation of the decline in electrode performance.
Electrode potential: switch the gear of the instrument to the mV range, put the electrode into the standard buffer solution with pH=6.86, the best value is around 0mV, and the maximum is within plus or minus 40mV. If it exceeds this range, the instrument will not be calibrated normally, and the calibration will be wrong.
6.86pH - 0mV plus or minus 40mV
9.18pH - around 120～130mV
4.00pH - around 170mV
2. How often does the pH electrode need to be calibrated?
It is recommended to calibrate once a day.
3. How to store the pH electrode?
When the electrode is not in use, it needs to be stored in 3mol/L potassium chloride solution (3M KCl);
4. How long is the life of the pH electrode?
Under normal use and proper maintenance, the life of the pH electrode is 1 year.
5. When measuring pH, the sample temperature is 10°C. Does the pH meter with automatic temperature compensation display the pH value at 10°C or 25°C?
The pH meter shows the pH value of the solution at the current temperature; if the sample temperature is 10°C, the pH meter shows the value of the solution at 10°C. The temperature compensation of the acidity meter refers to compensating the influence of temperature on the pH electrode, but it cannot compensate the pH value at any temperature to 25°C.
6. How long is the shelf life of pH buffer solution?
Generally, in the unopened state, the shelf life is 1 year. Once opened and used, due to the action of various molds and carbon dioxide in the air, it is easy to deteriorate. It is recommended to store the buffer solution in the refrigerator after opening, and it is recommended to store it for no more than one month.
7. Why can't the pH composite electrode be soaked in deionized water for a long time?
If the composite electrode is immersed in deionized water for a long time, the KCl concentration inside the liquid junction (such as inside the sand core) will be greatly reduced, and the potential of the liquid junction will increase, resulting in electrode instability.
8. How to operate if the external reference solution of the pH electrode is polluted?
For rechargeable electrodes, you can prepare a new KCl solution and add it in, pour it out after the first and second additions, so as to clean the inner cavity.
