Making use of ion fluxes through potentiometric sensor membranes: ISEs with step responses at critical ion activities

Ion-selective membrane electrodes (ISEs) were designed for which the ideal response to primary ions is switched on at a given critical sample activity . Only above this value, the sensors exhibit the conventional selectivity b ehavior dictated by the membrane components (ionophore, solvent), whereas, below the critical activity, they turn out to be completely non-specific an d yield apparent selectivity factors of about unity. ISEs of the novel type , so-called 'switchtrodes', were realized on the basis of Cu2+-selective io nophore membranes. The response curves of the sensors fully conformed to th e theoretical expectations, which opens interesting applications of such de vices for environmental monitoring. (C) 2001 Elsevier Science B.V. All righ ts reserved.