Measuring the pH of water from a water purification system can be problematic. Why is this

The objective of a water purification system is to produce a finished product of low ionic strength. This also means that there is low hydrogen ion concentration present, which can result in slow response times and inaccurate pH results if using a general-purpose pH electrode. The problem can be overcome by selecting an electrode that has the following characteristics:

• A diaphragm with a high outflow rate of electrolyte.
• An A glass membrane (gives a short response time in low ionic strength media).

The Schott Blueline 13 electrode combines both of these features in a laboratory electrode and is thus ideal for this application.