Membrane Systems for Piezoelectric and Electrochemical Sensing in Environmental Chemistry

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Abstract
This paper illustrates work at the University of Wales College of Cardiff (formerly UWIST) relating to the development and applications of membrane systems in various modes for possible use in environmental analysis. Three main types are illustrated, namely, membranes coated on quartz crystals for piezoelectric monitoring of gases and vapours, membranes used as the sensing components of potentiometric ion sensors, and catalytic enzyme membranes used for converting analyte components into suitable forms for electrochemical sensing. The piezoelectric type membranes are illustrated by modified cyclodextrins for detecting benzene, epoxyoctacosahydro[12]cyclacene derivatives for detecting nitrobenzene and other aromatic vapours, and pyridoxine hydrochloride for ammonia detection. Potentiometric ion-sensing, that is, ISE membranes, are illustrated by selected crown ethers as ionophores with tetraphenylborate for detecting the herbicides, diquat and paraquat. Finally, catalytic type membranes are illustrated by catalase and peroxidase-based membranes as modifiers for producing species in hydrogen peroxide monitoring that can avoid the interferences involved in the direct electrochemical detection of hydrogen peroxide.