The primary
outputting signal is possibly due to ions
accumulated at the ion-selective membrane
interface. Current flowing through the electrode is
equal to or near zero. The electrode follows the
presence of the monitored ion resulting from the
enzyme reaction (Kauffmann and Guilbault 1991).
For example, glucose oxidase can be immobilized
on a surface of the pH electrode. Glucose has only
minimal influence on pH in the working medium;
however, the enzymatically formed gluconate
causes acidification. A biorecognition element is
immobilized on the outer surface or captured inside