Art v1700383 ultrapure water ph measurement

Ordinarily pH measurements are made in water with 1,000 to 10,000 µS/cm conductivity. The conductivity comes from
dissolved solids which are typically salts but also acid or base. These dissolved substances are in the solution in ion form
which makes such solutions conducting. With conductivities of 1,000 µS/ cm or more, an ample supply of mobile ions
provides pH electrodes with a good electrical circuit to yield fast, accurate pH readings. In pure water with low
conductivity, standard pH electrodes exhibit less reliable results. They respond more slowly, drift, and do not reproduce
calibration results between buffers and grab sample. In “Ultrapure” water, pH electrodes become jumpy, flow sensitive
and inaccurate. To overcome these challenges, proper selection of the electrochemical cell elements in the pH sensor will
provide stable, accurate measurements.