Journal of Material Sciences & Engineering

Unintended Changes of Ion-Selective Membranes Compositionâ??Origin and Effect on Analytical Performance

Abstract

Agata Michalska, Krzysztof Maksymiuk , Emilia Stelmach

Ion-selective membranes, as used in potentiometric sensors, are mixtures of a few important constituents in a carefully balanced proportion.
The changes of composition of the ion-selective membrane, both qualitative and quantitative, affect the analytical performance of
sensors. Different constructions and materials applied to improve sensors result in specific conditions of membrane formation, in
consequence, potentially can result in uncontrolled modification of the membrane composition. Clearly, these effects need to be considered,
especially if preparation of miniaturized, potentially disposable internal-solution free sensors is considered. Furthermore, membrane
composition changes can occur during the normal operation of sensors—accumulation of species as well as release need to be taken into
account, regardless of the construction of sensors used. Issues related to spontaneous changes of membrane composition that can occur
during sensor construction, pre-treatment and their operation, seem to be underestimated in the subject literature. The aim of this work is
to summarize available data related to potentiometric sensors and highlight the effects that can potentially be important also for other
sensors using ion-selective membranes, e.g., optodes or voltammetric sensors.