Heterogeneous membrane electrodes development

The real move towards ISEs based on non glass membranes came in 1961 when Pungor and Hollos-Rokosinyi (1 6) produced a membrane by incorporating silver iodide into paraffin. This led on to the development of heterogeneous membrane electrodes, especially those based on silicone rubber matrices (17 -20). 

The parallel electrolytic reduction developments at Karlsruhe appear to have concentrated initially more on the reduction of Pu and U in electrode-equipped mixer-settlers in which the reduction occurred largely in the settled aqueous phase rather than in a heterogeneous mixture. It was determined that a separating membrane may njt be necessary because of the redox potentials in the U - U5 - U6 system and the absence of gaseous products at the electrodes which could lead to explosive mixtures. A pulsed column, with internals quite different from those of Allied Chemical s electropulse column, was eventually developed and successfully tested (15,26) (Fig. 4). 

Many enzyme immobilization techniques developed in connection with the preparation of heterogeneous biocatalysts have been applied for the construction of enzyme electrodes as well as for other types of biosensors. The immobilization of enzymes or other biocomponents on different membranes is most frequently realized by crosslinking agents, first of all by glutaraldehyde, and with the addition of bovine serum albumin [169] or other proteins, with l,8-diamino-4-aminomethyloc-tane, [170], etc. 

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