Installation
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MXD70 pH / Redox
Setup and Operating Guide
Installation
Care and Maintenance of pH / Redox Electrodes
All pH and Redox electrodes contain an electrolyte solution, gel or polymer that has a limited life in
both operation and on the shelf. The electrode shelf life depends on its storage conditions, it is
recommended that the electrode should be used within six to twelve months after purchase.
For gel filled, non-flow electrodes the storage boot may become dried out during storage. This can
result in evaporation of the water inside the electrode causing high impedance in the reference cell. If
allowed to fully dry out the operation of the electrode will be irreversibly damaged. For electrodes in
storage it is recommended that every three to four months the following procedure is carried out:
ï‚· Remove the black storage boot or transit cover at the end of the electrode
ï‚· Re-wet the fibre pack inside the storage boot with 3.8 Molar Potassium Chloride (KCl) saturated
solution or if this is not available use a quantity of 4pH buffer solution. Note do not use deionised
water.
ï‚· Re-seal the storage boot or transit cover.
For electrodes with soaker bottles ensure that the electrode is stored upright in the soaker bottle, and
replace the bottle solution with 3.8 Molar Potassium Chloride (KCl) saturated solution approximately
every 6 months.
Depending on the issue the following glass body pH electrode maintenance procedures can be carried
out:
 Initial Cleaning – Wash the electrode with a solution of liquid detergent and warm water by gently
scrubbing with a soft tooth brush or wet tissue. Follow this by thoroughly rinsing the electrode in
deionised water or clean tap water.
 Inorganic Scale Deposits – Dissolve the deposit by immersing the electrode bulb only in a solution
of dilute (10%) Hydrochloric Acid for a few minutes. Follow the supplier’s data sheet when
handling acids and dispose of as instructed by your local authority regulations.
 Organic Oil or Grease Films – Wash the electrode with a solution of liquid detergent and warm water
by gently scrubbing with a soft toothbrush or wet tissue. Follow this by soaking the pH electrode for
between 10 and 30 minutes in a 3.8 Molar KCl solution.
 Plugged or Dry Wick – Remove contaminate with one of the above cleaning procedures. Then soak
the electrode in an 80°C, 3.8 Molar KCl solution for 30 minutes. Before allowing the electrode to cool
in the same solution to promote flow of internal electrolyte through the liquid junction.
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