Potentiometric sensors

This chapter describes the functioning of potentiometric sensors, how they can be usefully employed, and in which experimental situations. Potentiometric sensors work through the measurement of an equilibrium potential, i.e. the potential at zero current, of the sensor versus a suitable reference electrode. These potentials are a function of the activity of the species in solution, not of their concentration. The Debye–Hückel equation relates concentrations to activities and can often be employed; indeed, potentiometric measurements can be used to test the Debye–Hückel theory. For potentiometric sensors to be useful, they must have a sufficiently fast response and be sufficiently selective in media containing various species, besides having a sufficiently good detection limit. The chapter then considers the functioning of ion-selective electrodes; the types of selective electrodes; miniaturisation strategies; and the criteria for choosing a potentiometric sensor.