How often is it recommended to change the storage solution for a pH probe?

Document ID

Document ID TE9684

Published Date

Published Date 04/03/2019
Question
How often is it recommended to change the storage solution for a pH probe?
Summary
Frequency of storage solution replacement.
Answer
The solution that the pH probe is stored in should be changed regularly. For waste water applications in particular it is extremely important. Over time bacteria will grow in the storage solution, eventually contaminating the internal electrolyte. Bacteria often produce acids as byproducts of their digestion, this acid causes an offset that causes buffers to not be recognized, leading to failed calibrations and overall a premature probe failure.

For refillable probes, replacing the filling solution can often fix this problem (see: What is the procedure for replacing the filling solution in a refillable pH probe?)
For non-refillable probes, the contaminated electrolyte cannot be replaced and therefore the complete probe would need to be replaced. (This would not be covered under warranty as the failure would be caused my improper maintenance, not by a manufacturing defect.)

It's recommended that the storage solution be changed weekly on average, for waste water applications changing even more frequently would be best.