Five Maintenance Tips for pH Meter
1. Storage of pH glass electrode
Short term: stored in a buffer solution with pH=4;
Long term: stored in a buffer solution with pH=7.
2. Cleaning of pH glass electrode
The contamination of glass electrode bubbles may prolong the electrode response time. Use CCl4 or soap solution to wipe away dirt, then immerse in distilled water for one day and night before continuing to use. When pollution is severe, soak in 5% HF solution for 10-20 minutes, rinse immediately with water, and then immerse in 0.1N HCl solution for one day and night before continuing to use.
3. Treatment of aging of glass electrodes
The aging of glass electrodes is related to the gradual changes in the adhesive layer structure. The old electrode has a slow response, high membrane resistance, and low slope. Etching off the outer layer of the adhesive layer with hydrofluoric acid can often improve electrode performance. If this method can be used to regularly remove the inner and outer adhesive layers, the lifespan of the electrode is almost infinite.
4. Storage of reference electrode
The best storage solution for silver silver chloride electrodes is saturated potassium chloride solution. High concentration potassium chloride solution can prevent silver chloride from precipitating at the liquid interface and maintain the liquid interface in working condition. This method is also applicable to the storage of composite electrodes.
5. Regeneration of reference electrode
The majority of problems with reference electrodes are caused by blockage at the liquid interface, which can be solved using the following methods:
(1) Soaking solution interface: Heat a mixture of 10% saturated potassium chloride solution and 90% distilled water to 60-70 ℃, immerse the electrode in about 5cm, and soak for 20 minutes to 1 hour. This method can dissolve the crystals at the electrode end.
(2) Ammonia immersion: When the liquid interface is blocked by silver chloride, concentrated ammonia water can be used for immersion. The specific method is to fill and clean the electrode, drain the liquid, and immerse it in ammonia water for 10-20 minutes, but do not let the ammonia water enter the inside of the electrode. Remove the electrode and wash it with distilled water. Add the filling solution again and continue to use.
(3) Vacuum method: Cover the reference electrode liquid junction with a hose, use a water flow suction pump to suction the partially filled liquid through the liquid junction, and remove mechanical blockages.
(4) Boiling liquid interface: The liquid interface of the silver silver chloride reference electrode is immersed in boiling water for 10-20 seconds. Note that the electrode should be cooled to room temperature before the next boiling.
(5) When the above methods are ineffective, mechanical methods such as sandpaper grinding can be used to remove blockages. This method may cause the ground sand particles to be inserted into the liquid interface, resulting in permanent blockage.
