In maintenance and storage of pH meters, which procedure shall not be done?

• A. To keep the electrode bulb moist during storage, store the electrode in distilled water.
• B. Rinse pH electrodes in between measurements.
• C. Blot the electrode dry after rinsing the pH electrodes.
• D. Mild soap solution may be used in general cleaning of the electrodes.

Answer: (A)

Keeping the pH electrode hydrated is essential, but storing the electrode in distilled water for an extended period is not recommended. Distilled water lacks ions and can cause dilution or imbalance of the electrode’s internal filling/ reference system, leading to unstable or drifted readings. The best practice is to store the electrode in the manufacturer's storage solution (often a saturated KCl or similar storage medium) or another appropriate storage buffer to maintain the correct ionic environment. Rinsing between measurements helps prevent carryover, blotting dry minimizes dilution of the next sample, and mild soap can be used for general cleaning as long as the electrode is thoroughly rinsed afterward.