As the WQ-pH sensor ages, it may exhibit sluggish or noisy readings. The following procedures may improve performance.
Reference Electrode Problems:
A blocked reference junction is the most common problem of pH measurements. Symptoms include a slow response, off-scale and noisy readings.
Soak the WQ-pH sensor in a beaker of warm water (50°C) for 15 minutes to remove dried gel or salts from the junction. Then place in a beaker of warm 4M KCl solution. Set aside until it returns to room temperature. The gel should be moist and the junction flow should be restored.
Glass Bulb Problems:
The glass bulb of the pH probe will get dirty over time. The following solutions may be used for cleaning:
Protein: Wash in a solution of liquid soap, (about 1⁄2 teaspoon per 200mL warm water), using a soft cloth to gently wipe the pH glass – remember that pH glass is extremely delicate and breaks very easily.
Inorganic Salts: Wash in 0.1M HCl or EDTA (DO NOT SOAK); rinse with distilled water.
Greasy Films: Wash in acetone or methanol (DO NOT SOAK); wash with liquid soap then rinse with distilled water. After cleaning, place the electrode in the sensor storage solution or pH 4 buffer for 15 minutes prior to use.
Between measurements, store the pH electrode in a beaker containing pH 4.00 buffer.
When storing for longer periods, store the pH electrode in the storage bottle that came with the electrode. The storage bottle should contain either commercially prepared storage solution, or a 1:1 solution of pH 4 buffer and 4M KCl. Ensure that the foam or cotton ball in the storage bottle is thoroughly wetted with storage solution to maintain a moist environment around the pH bulb and junction.
Do not store the electrode in distilled or deionized water – this will cause ions to leach out of the glass bulb and render the sensor useless. After storage, there may be may be white KCl crystals deposited on the electrode. Such salt formation will not interfere with measurements. Simply rinse the electrode with distilled water to remove the crystals and blot dry before use.