Preliminary note Ion-selective conductometric microsensors based on the phenomenon of specific salt extraction

Ion activity measurements in aqueous media are funda­mental to an extremely wide range of problems from cellmembrane transport studies to environmental monitoringand chemical oceanography. The use of potentiometricion-selectiveelectrodes (ISE) in these areas is now practi­cally indispensable. During the 1970s and 1980s a numberof approaches (e.g. ion-selectivefield-effecttransistors [1],coated-wire electrodes [2]) were proposed in order tominiaturise the ion-selectivesensors, simplify their fabrica­tion and extend the scope of their application. However,this drive for miniaturisation and integration was not fullyaccomplished, since the technical solution that would al­low the fabrication ofa solid-state,group-technology-com­patible reference electrode is not yet available, so singleprobe all-solid-statepotentiometric ion microsensors stillcannot be produced