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Avoid direct contact with the sensor. This causes damage, which will cause the pH meter to get large discrepancies. If contact is unavoidable, use soft paper to handle the probe (e.g. A tissue).

Rinse the probe well after each use with demineralized water. This is especially important when measuring aggressive materials or in solutions that contain heavy metals or proteins. This way you will remove residue from the probe which lessens your chances of damage.

Store the pH probe damp. This prevents contamination from drying onto the probe. Place some additive solution into the protective cap. Never use tap or demineralized water for this, neither are appropriate for this.

If there is contamination, clean the pH probe. The product to use depends on the type of contamination.

• Algae growth: use a light soap solution or alcohol. Do not completely immerse the probe, but dip 3-5 cm into the solution and let soak for 15 minutes.
• Fat and oil: use a water soluble organic cleaner, e.g. acetone. Rinse well afterwards with demineralized water.
• Protein: use a HCl/pepsin solution and let the pH probe soak for a few hours, then rinse well with demineralized water.

If your measurements are not stable you will need to calibrate your pH meter. You will determine the deviation of the pH meter by comparing values to international standard values, so will know how far out your meter is.

When it is no longer possible to calibrate your meter, the pH probe will need to be replaced. Ensure that the pH meter connector makes good contact and that the tester’s pawl matches the slot in the pH probe. If you don’t do this the meter won’t work properly. After replacing the pH probe you will need to calibrate the meter.

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