Use, maintenance and maintenance of pH electrode
1, the use of pH electrode
At present, most of the pH meter electrodes used in the laboratory are composite electrodes. Its advantages are convenient use, free from the influence of oxidation-reduction substances, and fast balance speed. Attention should be paid to the following items when using:
(1) When in use, the rubber sleeve and the rubber sleeve at the lower end of the pH electrode should be completely removed to keep the pressure difference of potassium chloride solution in the electrode. Check the bulb at the front end of the glass electrode before use. Under normal conditions, the electrode should be transparent and crack-free, and the bulb should be filled with solution, and no bubbles can exist.
(2) Generally, two-point calibration is adopted, with 6.86pH () as the first point and 4.00pH () or 9.18( )pH as the second point (note that the calibration value should be consistent with the standard value of the standard solution at the actual measured temperature). Make the pH value as stable as possible during calibration, and then press the Enter key.
(3) Generally, when the performance of pH electrode is good, the slope after calibration is above 98%, and the performance is slightly decreased by more than 95%. If it is lower than 90%, it is recommended to replace the electrode.
(4) In the calibration state, the slow and unstable reaction is the embodiment of the decline of pH electrode performance.
(5) The 5)pH composite electrode is not suitable for measuring organic matter, grease, viscosity and other substances.
(6) When using 6)pH composite electrode, the external reference is the most likely problem. The main reason for the error is the liquid junction of the electrode and the blockage at the liquid junction.
(7) When measuring the value of solution with pH electrode, it should be fully stirred, otherwise the reaction will be slow.
(8) In winter, when the ambient temperature reaches freezing point, the pH electrode cannot be used, which is prone to cold explosion. It is recommended to use it above.
2. Maintenance of pH electrode
(1) The connectors and sockets connected to the pH electrodes should be kept clean and dry, free from pollution, and ensure good contact. When there is pollution, 99% industrial alcohol can be used to wipe them.
(2) The pH electrode used for the first time (no solution in the sheath) or stopped for a long time must be soaked in 3mol/L potassium chloride solution for 24 hours before use.
(3) When measuring the solution with large concentration, shorten the measuring time as far as possible, and carefully clean it after use to prevent the solution to be measured from adhering to the pH electrode and polluting the electrode.
(4) The electrode should avoid being immersed in distilled water, protein solution and acidic fluoride solution for a long time, and the electrode should avoid contact with silicone oil.
(5) After measurement, the pH electrode should be inserted into the sheath containing potassium chloride solution, and the amount of potassium chloride solution in the electrode rod should be observed frequently, and it should be added in time, generally not less than half. Plug the upper plug when it is not measured.
