Standard Operating Procedure for Use and Maintenance of pH Meters
At present, the electrodes used in the laboratory are composite electrodes, which have the advantages of being easy to use, not affected by oxidizing or reducing substances, and having a fast equilibrium speed. When in use, remove the rubber sleeves from the electrode filling port and the lower end to maintain the hydraulic pressure difference of the potassium chloride solution inside the electrode. Below is a brief introduction to the use and maintenance of electrodes:
1. When the composite electrode is not in use, it can be fully immersed in 3M potassium chloride solution. Do not soak in detergent or other absorbent reagents.
2. Before use, check the bulb at the front end of the glass electrode. Under normal circumstances, the electrode should be transparent and free of cracks; The bubble should be filled with solution and there should be no bubbles present.
3. When measuring solutions with high concentrations, try to shorten the measurement time as much as possible, clean carefully after use, and prevent the measured liquid from adhering to the electrode and contaminating it.
4. After cleaning the electrode, do not wipe the glass film with filter paper, but use filter paper to absorb dry to avoid damaging the glass film, preventing cross contamination, and affecting measurement accuracy.
5. During measurement, pay attention to the silver chloride internal reference electrode of the electrode, which should be immersed in the chloride buffer solution inside the bulb to avoid the phenomenon of digital jumping in the display part of the meter. When using, be careful to gently shake the electrode a few times.
6. The electrode cannot be used for strong acids, strong bases, or other corrosive solutions.
7. It is strictly prohibited to use in dehydrated media such as anhydrous ethanol, potassium dichromate, etc.
Preparation and storage of standard buffer solution
1. pH standard substances should be stored in a dry place. For example, mixed phosphate pH standard substances will undergo deliquescence when the air humidity is high. Once deliquescence occurs, pH standard substances cannot be used.
2. Secondary distilled water or deionized water should be used to prepare pH standard solutions. If it is used for measuring pH at level 0.1, ordinary distilled water can be used.
3. The pH standard solution should be diluted using a smaller beaker to reduce the amount of pH standard solution sticking to the beaker wall.
4. Plastic bags or other containers used to store pH standard substances should not only be emptied clean, but also rinsed multiple times with distilled water, and then poured into the prepared pH standard solution to ensure its accuracy.
5. The prepared standard buffer solution can generally be stored for 2-3 months. If turbidity, mold or precipitation is found, it cannot be continued to be used.
6. The alkaline standard solution should be stored in a sealed polyethylene bottle. Prevent carbon dioxide from entering the standard solution and forming carbonic acid, reducing its pH value.
