Use and maintenance of composite electrode The composite electrode is an important component of this type of pH meter. Its normality is directly related to the accuracy of the measured data. The following attention should be paid to the daily operation and maintenance. First of all, the composite electrode should be discarded in time when it is full 2a or used for 1a. Second, before using the composite electrode, the sensitive glass bulb of the electrode should be checked. Under normal circumstances, the electrode should be transparent and free of cracks; the sphere should be filled with solution without air bubbles, otherwise it will affect the measurement accuracy. If there are air bubbles, the internal air bubbles should be removed like a thermometer. Since the glass bulb is very thin, any breakage will render the electrode useless. When it is confirmed that everything is normal, remove the electrode protective cover, avoid contact with the sensitive electrode glass bulb and hard objects during operation, and avoid long-term immersion in distilled water, protein solution and acidic fluoride. When in use, the rubber plug at the top of the composite electrode should be removed; the height of the filling liquid inside the electrode is generally 2/3. If the filling liquid is too small, an external reference supplementary solution of saturated potassium chloride should be added. After cleaning the electrode, do not wipe the glass membrane with filter paper, use filter paper to absorb moisture to prevent cross-contamination and damage to the glass membrane. In addition, the terminal of the composite electrode must be kept clean and dry to prevent short circuit at both ends of the output, otherwise it will cause measurement inaccuracy or failure. At the end of the measurement, the electrode protection should be put on in time, and a small amount of external reference supplement should be placed in the electrode sleeve to keep the electrode bubbles moist. If the composite electrode is not used for a long time (more than two weeks), before using it again, the measuring end of the electrode should be immersed in a 3mol/L potassium chloride solution to activate it for more than 2 hours, otherwise it will cause potential drift. Finally, the most common problem of the composite electrode is the clogging of the liquid boundary of the external reference electrode, which should be cleaned in time, otherwise it is easy to produce data errors.
