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109117-1 Rev. A, 10/96
3
3.4.4 Electrode Problem Solving (cont)
2. Non aqueous samples (organics) do not follow the normal
pH scale and can cause some measuring problems. These
solutions are usually low in ionic strength, may dehydrate
the pH membrane and often cause the junction to plug due
to incompatibility with the electrode fill solution. The most
reliable way to pH organics is to dilute them with water
until stable readings can be generated.
3. Concentrated samples can cause pH measuring errors.
This is caused by problems with the pH sensing glass and
its ability to distinguish the Hydrogen ion activity over the
mass of other ions in the sample. The creation of new
junction potentials due to KCl dissociation problems can
also cause instability. The best solution is to dilute the
samples into measurable ranges.
For more information refer to the Corning Guide to pH
Measurement.
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