accumet AE150 pH Benchtop Meter
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Electrode Cleaning and Rejuvenation
pH electrodes that are functioning properly or have not been in use for a period of time may
be restored to normal performance by one or a combination of following procedures:
Salt deposits – dissolve the salt deposits by immersing the electrode in a container filled with
warm tap water for ten to fifteen minutes and then thoroughly rinse it with deionized water.
Oil/grease films – wash the pH electrode bulb in mild detergent and water and then rinse the
electrode tip with deionized water.
Clogged reference junction – heat a dilute 1% KCl solution to 60 °C. Place the sensing
portion of the pH electrode into the heated KCl solution for approximately 10 minutes.
Care
must be taken when performing this procedure.
Allow electrode to cool while immersing it in
an unheated KCl solution.
Protein deposits – use protein cleaning solution to remove any protein that is deposited onto
pH electrode. Allow the electrode to stand in the cleaning solution for five to ten minutes.
pH Electrode Rejuvenation
Caution:
Proper protective eyewear and precautionary measures must be used when
performing the rejuvenation, as it involves the use of concentrated acid and alkaline.
Generally, if the storage and maintenance procedures have been closely followed, the pH
electrode can be used immediately. However, should the electrode response become
sluggish, it may be possible that the glass bulb has dehydrated. Immersing the electrode in
storage solution for 1- 2 hours can rehydrate the glass bulb. If this fails, the electrode may
require rejuvenation. At no time should you touch or rub the glass bulb, as this causes the
build-up of electrostatic charge. If cleaning procedures do not re-activate the electrode to
acceptable status, try rejuvenating the electrode using the following procedure.
1. Dip and stir the electrode in a concentrated acid (i.e. HCl, H
2
SO
4
) for 5 minutes.
2. Leave the electrode in tap water for 15 minutes.
3. Dip and stir the electrode in a strong base (NaOH) for 5 minutes.
4. Leave the electrode in tap water for 15 minutes.
5. If the electrode is refillable, remove the old electrolyte and add new electrolyte.
6. Test the pH electrode with standard calibration buffer solutions.
7. If needed, repeat the rejuvenation procedure up to 3 times. If the response does not
improve, the electrode has completed its useful life. Replace it with a new electrode.
