Solution to common problems with pH meters!
1. Do two measurements of the same sample have different pH values?
Temperature changes or chemical reactions occurring in the sample itself can cause changes in pH value. Therefore, it is important to maintain a consistent temperature and avoid chemical reactions.
2. Is the reading inconsistent when measuring the same sample on two pH meters simultaneously?
Due to the different calibration conditions of the two pH meters (such as calibration performed at different times), there are differences in the measured values. So it is necessary to calibrate the pH meter using the same buffer at the same time, and then measure it simultaneously.
3. Why is it that the buffer has deteriorated within its validity period and cannot be used?
The shelf life of the buffer solution refers to the shelf life when it is not opened for use. Once opened for use, the buffer is prone to deterioration due to the effects of various molds in the air.
Attention: Never pour the used buffer back into the original bottle!
4. How often does the electrode need to be calibrated?
The frequency of electrode calibration depends on the specific conditions of electrode use, maintenance, sample properties, and measurement accuracy. It is recommended to calibrate once a day, with a maximum of once a week. Replacing electrodes and not using them for a long time require calibration before use.
5. How to maintain the pH electrode?
After using the electrode for a period of time, if the slope decreases or the response speed slows down, the following methods can be tried:
① If the measured sample contains protein, the electrode membrane can be cleaned with Pepsin/hydrochloric acid lotion.
② If the measured sample is an oily/organic liquid, it can be rinsed with acetone or ethanol.
③ If it is found that the electrode solution has become dirty and black, a thiol cleaning solution can be used to clean the solution solution solution.
④ Activate the electrode membrane. Activation method: Soak the electrode regeneration solution for 30 seconds, and then soak it in 3mol/L KCl solution for 5 hours.
6. The sample temperature is 10 ℃, and is the pH value displayed on the instrument at 10 ℃ or 25 ℃?
The pH meter displays the pH value of the solution at the current temperature. If measured at 10 ℃, the instrument displays the value of the solution at 10 ℃. If a pH of 25 ℃ is required, the solution temperature must be raised/lowered to 25 ℃ before measurement. The temperature compensation of the pH meter refers to compensating for the influence of temperature on the pH electrode, but it cannot compensate for the pH value at any temperature to 25 ℃.
7. Why does the electrode display 7.02 after calibration in a pH 7.00 buffer solution?
At this point, the buffer temperature is around 20 ℃. Due to the slight change in pH value of buffer solution with temperature, 7.00 is only the value of buffer solution at 25 ℃, while the value of buffer solution at 20 ℃ should be 7.02. The pH meter can automatically compensate for the impact of temperature on the buffer solution to ensure measurement accuracy.
