Collect. Czech. Chem. Commun. 1991, 56, 178-191

Ion-selective electrode and enzyme sensors for flow-type environmental analysis

J. D. R. Thomas

School of Chemistry and Applied Chemistry, University of Wales College of Cardiff, PO Box 912, Cardiff CF1 3TB, Wales, U.K.


Illustrative examples from researches in the author’s laboratories are given of potentiometric ion-selective electrodes (ISEs) and catalytic membrane amperometric electrodes suitable for environmental analysis. The uses of sulphide ISEs are demonstrated for monitoring the activities of sulphate-reducing bacteria, in effluent analysis for sulphide, and in process/effluent analysis for sulphide, thiols and polysulphides. Diquat and paraquat ISEs are discussed in relation to their optimisation in terms of appropriate crown ether and ion-pairing agents, together with prospects of their uses. Catalytic membrane systems for use in electrochemical analysis may be based on metal oxide catalysts or enzymes. The best of the new metal oxide catalysts for hydrogen peroxide analysis in association with an oxygen electrode is based on manganese dioxide and offers an alternative to lead dioxide and catalase. An alternative membrane system for use with a platinum electrode is peroxidase in association with a mediator in order to permit a low potential approach for hydrogen peroxide sensing. Hydrogen peroxide is a product of many oxidase catalysed reactions and its electrochemical detection permits the analysis of a wide range of substrates, illustrated here for glucose in various food products and hypoxanthine in the spoilage of fish meats.