Common problems and solutions of pH meter
1 The same sample, the pH value of the two measurements is not the same?
Changes in temperature or chemical reactions in the sample itself can cause changes in pH. Therefore, try to keep the temperature consistent and avoid chemical reactions.
2 The same sample is measured on two pH meters at the same time, but the readings are inconsistent?
Due to the different calibration conditions of the two pH meters (such as calibration done at different times), there are differences in the measured values. Therefore, the pH meter should be calibrated at the same time with the same buffer, and then measured at the same time.
3 Why the buffer solution has deteriorated within the validity period and cannot be used?
The validity period of the buffer solution refers to the storage period in the unopened state of use. Once opened and used, the buffer solution is more likely to deteriorate due to the action of various molds in the air.
4 How often do electrodes need to be calibrated?
The frequency of electrode calibration depends on specific conditions such as electrode use, maintenance, sample properties, and measurement accuracy. It is recommended to calibrate once a day, and the longest should not exceed once a week. When replacing electrodes or not using for a long time, it must be calibrated before use.
5 How to maintain the pH electrode?
After using the electrode for a period of time, if you find that the slope becomes lower and the response speed becomes slower, you can try the following methods:
① If the measured sample contains protein, the electrode membrane can be cleaned with pepsin/hydrochloric acid washing solution.
② If the measured sample is oily/organic liquid, it can be rinsed with acetone or ethanol.
③ If the junction of the electrode is found to be dirty and black, the junction can be cleaned with mercaptan cleaning solution.
④ Activate the electrode membrane. Activation method: soak in electrode regeneration solution for 30 seconds, then soak in 3mol/L KCl solution for 5 hours.
6 The temperature of the sample is 10°C. At this time, does the meter display the pH value at 10°C or 25°C?
The acidity meter shows the pH value of the solution at the current temperature. If it is measured at 10°C, the meter displays the value of the solution at 10°C. If it is necessary to obtain a pH of 25°C, the temperature of the solution must be raised/lowered to 25°C, and then Take measurements. The temperature compensation of the pH meter refers to compensating the effect of temperature on the pH electrode, but it cannot compensate the pH value at any temperature to 25°C.
