A C&EN Feature: Ion-Selective Electrodes

The single most important factor in the revitalization of analytical potentiometry has been the development of novel ion-selective electrodes. Ten years ago, few chemists predicted that electrodes specific for more than a dozen ions would join the pH-type glass electrode in commercial production and widespread use by 1967. These electrodes measure directly the activity (rather than concentration) of an ion in solution. They are nondestructive, portable, easy to use, and relatively inexpensive—about $30 to $145. They are now used in clinical analysis, water analysis and oceanographie research, process control, and in routine laboratory analytical determinations. Although isolated workers such as B. Lengyel and E. Blum predicted glass electrodes sensitive to metal ions more than 30 years ago, little progress was made as long as most chemists regarded the glass electrode as a membrane preferentially permeable to the hydrogen ion. Not until the tracer experiments of K. Schwabe and H. Dahms and the systematic ...