How to use a general pH meter correctly
The pH meter, abbreviated as pH meter, consists of two parts: an electrode and an electrometer. If the electrodes can be properly maintained, standard buffer solutions can be prepared according to requirements, and the electrometer can be operated correctly during use, it can greatly reduce pH indication errors, thereby improving the reliability of chemical experiments and medical testing data.
1, Proper use and maintenance of electrodes. Currently, the electrodes used in laboratories are composite electrodes, which have the advantages of easy use, unaffected by oxidizing or reducing substances, and fast equilibrium speed. When using, remove the rubber sleeve on the electrode filling port and the rubber sleeve at 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:
When the composite electrode is not in use, it can be fully immersed in a 3M potassium chloride solution. Avoid soaking with 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.
When measuring solutions with high concentrations, try to shorten the measurement time as much as possible. After use, clean carefully to prevent the measured solution from adhering to the electrode and contaminating it.
4. After cleaning the electrodes, do not use filter paper to wipe the glass film. Instead, use filter paper to absorb it dry to avoid damaging the glass film, preventing cross contamination, and affecting measurement accuracy.
During measurement, pay attention to the silver chloride internal reference electrode of the electrode. The electrode should be immersed in the chloride buffer solution inside the bulb to avoid the occurrence of digital jumping in the display part of the electrometer. When using, be careful to gently shake the electrode a few times.
6. Electrodes should not be used in strong acids, bases, or other corrosive solutions.
7. It is strictly prohibited to use in dehydrating media such as anhydrous ethanol, potassium dichromate, etc.
2, Preparation and preservation of standard buffer solution
1. pH standard substances should be stored in a dry place. For example, mixed phosphate pH standard substances may undergo deliquescence when the air humidity is high. Once deliquescence occurs, pH standard substances cannot be used.
2. When preparing pH standard solutions, secondary distilled water or deionized water should be used. If it is used for measuring pH with a 0.1 level pH meter, ordinary distilled water can be used.
3. When preparing a pH standard solution, a smaller beaker should be used to dilute it to reduce the amount of pH standard solution adhering to the beaker wall. Plastic bags or other containers for storing pH standard substances should not only be emptied clean, but also be rinsed multiple times with distilled water, and then poured into the prepared pH standard solution to ensure its accuracy.
4. The prepared standard buffer solution can generally be stored for 2-3 months. If turbidity, mold, or precipitation are found, it cannot be used again.
Alkaline standard solution should be stored in a sealed polyethylene bottle. Prevent carbon dioxide from entering the standard solution to form carbonic acid and reduce its pH value.
