Why for ultra-pure water and dirty water is a pH electrode with strong diffusion recommended?

Document ID

Document ID TE11107

Version

Version 2.0

Status

Status Published

Published Date

Published Date 03/14/2019
Question
Why for ultra-pure water and dirty water is a pH electrode with strong diffusion recommended?
Summary

pH probe recommendations

Answer

For ultra-pure water, as for dirty water, pH measurement requires an electrode with a liquid junction (annular ring or glass sleeve) that diffuses a lot.

For dirty water, it will avoid electrode contamination. The impurities will not penetrate the electrode because of the higher outflow at the liquid junction.

For pure waters, it is to have a faster response.

The high diffusion liquid junctions make it possible to establish a concentration gradient of KCl at the interface between the junction and the pure water. This makes the transition of ionic strength much less brutal, and thus reduce the junction potential to a minimal value, while stabilizing the measurements.

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