Problems that should be paid attention to when using PH meter
A, before the operation, should first check the integrity of the electrode. At present, most of the electrodes used in PH meters are composite electrodes, while the old generation of pH meters still use glass electrodes and calomel electrodes. Because the composite electrode is widely used, the composite electrode is mainly discussed below.
Calibration, calibrate the instrument according to the instrument instructions, and adjust the liquid to be tested and the standard buffer solution to the same temperature. Firstly, insert the electrode into the standard buffer solution whose PH difference with the tested sample is not more than two PH units, start the reading switch, adjust the positioner to make the reading just the PH of the standard solution, and repeat several times to make the reading stable. Take out the electrode and wash it, and then insert it into * * standard buffer solutions. After the instrument is accurate, it can be used to determine the sample.
Second, the main steps of using the acidity meter:
1. Turn on the power switch for preheating.
2, temperature compensation.
3. Use standard solution for positioning.
4. Use standard solution for slope correction.
5. measure ph.
Third, matters needing attention:
1. The newly used glass electrode should be soaked in distilled water and activated for 48h before use.
2. The bulb wall of the glass electrode is very thin, so it should be doubly protected when used.
3. The solution to be tested should be at the same temperature as the standard solution buffer solution, otherwise it needs to be compensated and adjusted again.
4 When replacing the solution to be tested, the electrode must be washed and dried.
At present, there are mainly two kinds of composite electrodes used in the laboratory: fully enclosed and non-enclosed, and the fully enclosed ones are relatively few, mainly produced by foreign enterprises. Before using the composite electrode, first check whether the glass bulb is cracked or broken. If not, it is generally considered that it can be used when the positioning and slope buttons can be adjusted to the corresponding pH value when two-point calibration is carried out with pH buffer solution, otherwise, the electrode can be activated according to the instruction manual.
After the measurement is completed, the rubber should be restored and the small hole should be sealed. After the electrode is cleaned by distilled water, it should be soaked in 3mol/L potassium chloride solution to keep the electrode bulb moist. If the protective solution is found to have been lost before the electrode is used, it should be soaked in 3mol/L potassium chloride solution for several hours to make the electrode reach a good measurement state. In practical use, it is found that some analysts treat the composite electrode as a glass electrode and soak it in distilled water for a long time, which is incorrect. This will greatly reduce the concentration of potassium chloride solution in the composite electrode, which will lead to the electrode's insensitive response during measurement and eventually lead to inaccurate measurement data. Therefore, the composite electrode should not be soaked in distilled water for a long time.
