Cleaning pH Electrodes

If you are noticing slower response times when using your pH electrode, check for visible build up of material on the glass membrane bulb. Electrodes which have no broken parts, and have not been allowed to dry out can often be restored to normal performance by one of the following procedures:

General Cleaning:
  • Soak the electrode in a 1:10 dilution of household bleach and 0.1 to 0.5% liquid detergent solution in hot water with vigorous stirring for 15 minutes.
  • Place junction under warm, running tap water for 15 seconds.
  • If it is a refillable electrode, drain/refill the reference chamber.
  • Soak the electrode in storage solution for at least 10 minutes.
Salt Deposits:
  • Dissolve the deposit by immersing the electrode in 0.1 M HCl for 5 minutes, followed by immersion in 0.1 M NaOH for 5 minutes, and thorough rinsing with deionised water.
Oil/Grease Films:
  • Wash electrode bulb in mild non-ionic surfactant, acetone or methanol, then rinse tip with deionised water.
Protein Deposits:
  • Dissolve the deposit by immersing the electrode in a 1% pepsin solution in 0.1 M HCl for five minutes, followed by thorough rinsing with deionised water.
Clogged Reference Junction:
  • Place the electrode into diluted KCl solution (electrode storage solution) heated to 60-80ºC and allow the electrode to cool in the solution.
  • For more severe clogging, use a solvent specific to the clogging material.
  • Alternatively, soak the electrode in a 0.1M HCl solution overnight.

Be careful not to break the glass membrane. The glass is thin and delicate but strong enough to handle aggressive cleaning with a cloth. Following cleaning, thoroughly rinse with deionised water and soak in the storage solution overnight, and always calibrate the pH meter after cleaning.

Storing pH electrodes

Always store your pH electrode after your series of tests are done as they need to be kept wet to maintain the glass membrane. The best method is to store it in the same solution as the reference electrolyte of your electrode, which for most common probes is 3M KCl.

If the glass membrane is allowed to completely dry out, the pH electrode will start to show slow response and fluctuations in readings. This drying process does take some time, so if you find a probe has been left out for a few days, it is possible to regenerate it simply by soaking it in the storage solution. For more severe cases of drying, one regeneration method is to store the electrode in 0.1M HCl overnight then in pH 4 buffer overnight again.

Never store the electrode in deionised water as this will dilute the electrode electrolyte through osmosis, and will lead to a slower response and lower accuracy. Rinsing your electrode with deionised water is fine, but it should not be used for storage. If you do not have any storage solution, then you can use a pH 4 buffer as a temporary replacement.

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