The PH meter is one of the commonly used equipment in the laboratory. Today I have compiled some maintenance and maintenance methods for the PH meter.
Maintenance method of ph meter:
1. The short-term storage of the pH glass electrode: stored in a buffer solution of pH = 4; long-term: stored in a buffer solution of pH = 7.
2. Cleaning of pH glass electrode The contaminated glass electrode bulb may make the electrode response time longer. You can use CCl4 or soap to wipe off the dirt, and then immerse it in distilled water for one day and night to continue to use. When the pollution is serious, use 5% HF solution for 10 to 20 minutes, rinse with water immediately, and then immerse in 0.1N HCl solution for one day and night to continue using.
3. Treatment of glass electrode aging The aging of glass electrodes is related to the gradual change of the glue layer structure. The old electrode has a slow response, high membrane resistance, and low slope. Etching the outer adhesive layer with hydrofluoric acid often improves the electrode performance. If this method can be used to regularly remove the inner and outer adhesive layers, the life of the electrode is almost unlimited.
4. Storage of reference electrode-The best storage solution of silver chloride electrode is saturated potassium chloride solution. High concentration potassium chloride solution can prevent the precipitation of silver chloride at the liquid junction and keep the liquid junction working status. This method is also suitable for the storage of composite electrodes.
5. Regeneration of the reference electrode The vast majority of problems that occur with the reference electrode are caused by clogging of the liquid junction, which can be solved by the following methods:
(1) Soaking liquid junction: use a mixed solution of 10% saturated potassium chloride solution and 90% distilled water, heat to 60-70 ° C, immerse the electrode for about 5 cm, and soak for 20 minutes to 1 hour. This method can dissolve the crystal at the end of the electrode.
(2) Ammonia immersion: when the liquid junction is blocked by silver chloride, it can be immersed in concentrated ammonia water. The specific method is to fill the electrode and wash it, immerse the solution in ammonia water for 10 to 20 minutes, but do not let the ammonia enter the electrode. Take out the electrode and wash it with distilled water, re-add the inner filling liquid and continue to use.
(3) Vacuum method: put the hose around the liquid junction of the reference electrode, use a water flow suction pump, suck the filling liquid through the liquid junction, and remove the mechanical blockage.
(4) Boiling liquid junction: The liquid junction of the silver-silver chloride reference electrode is immersed in boiling water for 10 to 20 seconds. Note that before the next boiling, the electrode should be cooled to room temperature.
(5) When the above methods are invalid, the mechanical method of sandpaper grinding can be used to remove the blockage. This method may cause the ground sand to be stuffed into the liquid junction. Cause permanent blockage.
PH meter maintenance method:
At present, the electrodes used in the laboratory are all composite electrodes. Its advantage is that it is easy to use, not affected by oxidizing or reducing substances, and has a fast balancing speed. When in use, remove the rubber sleeve on the electrode filling port and the rubber sleeve on the lower end to keep the hydraulic pressure difference of the potassium chloride solution in the electrode. The following is a brief introduction to the use and maintenance of electrodes:
â’ˆWhen the composite electrode is not used, it can be fully immersed in 3M potassium chloride solution. Do not dip with washing solution or other absorbent reagents.
â’‰Before using, check the bulb on the front of the glass electrode. Under normal circumstances, the electrode should be transparent without cracks; the bulb should be filled with the solution, and there should be no bubbles.
â’ŠWhen measuring a solution with a large concentration, try to shorten the measurement time as much as possible, and wash it carefully after use to prevent the measured liquid from adhering to the electrode and contaminating the electrode.
â’‹After cleaning the electrode, do not wipe the glass film with filter paper, but apply filter paper to dry it, to avoid damage to the glass film, prevent cross-contamination, and affect the measurement accuracy.
â’ŒPay attention to the electrode's silver-silver chloride internal reference electrode during the measurement should be immersed in the chloride buffer solution in the bulb to avoid digital jumps in the display part of the meter. When using, pay attention to gently shake the electrode a few times.
â’The electrode can not be used for strong acid, strong alkali or other corrosive solution.
â’ŽIt is strictly forbidden to use in dehydrating media such as absolute ethanol, potassium dichromate, etc.
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