Abstract

The measurement of pH is arguably the most widely performed test in the chemical laboratory, reflecting the importance of water as a ubiquitous solvent and reactant. In the 90 years since the first use of an electrode to determine hydrogen ion concentration, the glass electrode and its variants have matured into routine tools of analytical and process chemists. Yet, there continue to be developments that promise to broaden the scope and reach of these measurements. Among recent developments are miniature pH-sensitive field-effect transistors (pHFETs) being incorporated into pocket-sized pH “pens,” metal/metal oxide pH sensors for measurements at high temperatures and pressures, and flexible fiber-optic pH sensors for measuring pH within the body. This chapter discusses electrochemical and optical methods for pH measurement and is by necessity limited in scope; readers interested in a more comprehensive treatment may wish to refer to the recent text by Galster [1].