pH Electrode Maintenance

How do I maintain, store, and restore my PASCO pH electrodes?

Cleaning

For most applications, hot water rinse with domestic cleaning detergent can be used for cleaning. The following table contains specific cleaning recommendations for different types of solutions the probe is exposed to.

Solution Type	Recommended Cleaning Solution
limes and hydroxides	5-10% hydrochloric acid
organic fouling agents (fats, oils)	rubbing alcohol or liquid dish soap (soak in a warm water solution with soap)
algae and bacteria	diluted chlorine bleach

Storage

For best results, the pH soaker bottle should be filled with a pH electrode storage solution (SC-3507).

Do not store the electrode in distilled water as this will decrease the life of the electrode.

You may also make your own electrode storage solution of 4 M KCl with the following recipe:

To prepare 4M Potassium Chloride (KCl) electrode storage solution

• Weigh accurately 29.82 g of KCl
• Dissolve KCl in 80 ml of distilled water in a volumetric flask
• Mix - (You may heat the solution during mixing - 99°C)
• Once the KCl has completely dissolved or the solution is saturated, add distilled water up to 100 ml and properly mix it.

Removing Air Bubbles

Unstable readings may be caused by air bubbles attached to the inner electrode of the probe. To remove these bubbles, hold the electrode firmly by the handle and swing it quickly in an arc several times. If you still cannot eliminate the air bubbles, heat the electrode to 50-60 Celsius in tap water. Grab the electrode with an insulating glove or towel and shake it vigorously again

Restoration Procedure: Electrode is unresponsive

If the electrode is not responding quickly:

1. Soak the electrode in 1 M NaOH (sodium hydroxide) (40 g/L) for one minute. Rinse completely.
2. Soak the electrode in 1 M HCl (hydrogen chloride) for one minute. Rinse completely.
3. Soak the electrode in 0.1 M Hydrochloric Acid (HCl) for 15 minutes. Rinse completely.
4. Soak the electrode in a pH 7 buffer solution for 30 minutes. Rinse.
5. Try to calibrate the sensor to pH 4 and pH 10. If the electrode will not calibrate or hold the calibration, it should be replaced (PS-2573 pH Electrode)