Activation and maintenance of the pH meter
1. Activation
1. Soak the ph meter (acidity meter) electrode regeneration solution (ME51340073) for 30 seconds, then soak in 3mol/L KCl solution for 5 hours
2. pH meter (acidity meter) electrode, ph meter, ph electrode, acidity meter, acidity meter electrode
How to store the electrode of ph meter (acidity meter):
When the electrode is not in use, please store it in 3mol/L potassium chloride solution (3MKCl); it can be stored in pH7.00 buffer solution for a short time. Drying or immersing the pH meter (acidity meter) electrode in distilled water for a long time will shorten the service life of the electrode. When the composite electrode is not in use, it can be fully immersed in 3M potassium chloride solution. Do not soak with washing liquid or other water-absorbing agents. Check the bulb on the tip of the glass electrode before use. Under normal circumstances, the electrode should be transparent without cracks; the bulb should be filled with solution without air bubbles. When measuring a solution with a high concentration, 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 polluting the electrode. After cleaning the electrode, do not wipe the glass membrane with filter paper, but use filter paper to dry it, so as to avoid damage to the glass membrane, prevent cross-contamination, and affect the measurement accuracy. During the measurement, pay attention to the silver-silver chloride internal reference electrode of the electrode should be immersed in the chloride buffer solution in the bulb to avoid digital jumping in the display part of the electric meter. When using, pay attention to gently shake the electrode a few times. Electrodes cannot be used with strong acids, strong bases or other corrosive solutions. It is strictly forbidden to use in dehydrating medium such as anhydrous ethanol, potassium dichromate, etc.
At the same time, there are some things to pay attention to:
Glass electrodes must be soaked in distilled water for more than a day and night before the first use, and should be soaked in distilled water at ordinary times for ready use at any time. The glass electrode should not be in contact with strong water-absorbing solvents for too long. It should be operated as soon as possible when used in a strong alkali solution. After use, it should be washed with water immediately. For oily stains, use alcohol first, then carbon tetrachloride or hexyl ether, and finally soak in alcohol, then wash with distilled water. If the pH of the protein-containing solution is measured, the surface of the electrode is contaminated by protein, resulting in unreliable and unstable readings, and errors occur. At this time, the electrode can be corrected by soaking the electrode in dilute HCl (0.1mol/L) for 4-6 minutes . After the electrode is cleaned, it can only be blotted gently with filter paper. Do not wipe it with a cloth, which will cause static electricity on the electrode and cause incorrect readings. When using the calomel electrode, pay attention that the electrode should be filled with potassium chloride solution, and there should be no air bubbles to prevent open circuit. There should be a small amount of potassium chloride crystals to keep the solution saturated. When in use, remove the rubber plug on the top of the electrode, and a small amount of potassium chloride solution will flow out from the capillary to make the measurement results reliable. In addition, the accuracy of pH determination depends on the accuracy of standard buffers. The standard buffer solution used in the pH meter requires greater stability and less temperature dependence.
2. Maintenance
1. Storage of pH glass electrodes
Short-term: store in buffer solution with pH=4;
Long-term: Store in buffer solution with pH=7.
2. Cleaning of the pH glass electrode
Contamination of the glass electrode bulb may prolong the electrode response time. The dirt can be wiped off with CCl4 or soap solution, and then soaked in distilled water for a day and night before continuing to use. When the pollution is serious, it can be immersed in 5% HF solution for 10-20 minutes, rinsed with water immediately, and then immersed in 0.1N HCl solution for a day and night before continuing to use.
3. Treatment of glass electrode aging
The aging of the glass electrode is related to the gradual change of the glue layer structure. Older electrodes have sluggish response, high membrane resistance, and low slope. Etching off the outer adhesive layer with hydrofluoric acid often improves 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 for silver-silver chloride electrode is saturated potassium chloride solution. High-concentration potassium chloride solution can prevent silver chloride from precipitating at the liquid junction and keep the liquid junction in working condition. This method is also applicable to the storage of composite electrodes.
5. Regeneration of reference electrode
Most of the problems of the reference electrode are caused by the blockage of the liquid junction, which can be solved by the following methods:
(1) Soaking liquid junction: use a mixture of 10% saturated potassium chloride solution and 90% distilled water, heat to 60-70°C, immerse the electrode about 5cm, and soak for 20 minutes to 1 hour. This method can dissolve the crystals at the end of the electrode.
(2) Ammonia soaking: When the liquid junction is blocked by silver chloride, it can be soaked with concentrated ammonia water. The specific method is to clean the inside of 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. Take out the electrode and wash it with distilled water, and then add the filling liquid again and continue to use it.
(3) Vacuum method: put the hose around the liquid junction of the reference electrode, use a water flow suction pump, and the liquid in the suction part passes through the liquid junction to remove mechanical blockages.
(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 the electrode should be cooled to room temperature before the next boil.
(5) When the above methods are ineffective, the mechanical method of sandpaper grinding can be used to remove the blockage. This method may cause the grit under grinding to plug into the liquid junction. cause permanent blockage.
