ABSTRACT
Potentiometric enzyme electrodes are analytical devices that incorporate a biological or biologically derived sensing element intimately associated with a physiochemical transducer and may be classified among the growing area of biosensors. Products of the enzymatic reaction that may modify the redox state of the surface, such as hydrogen peroxide and protons, have been suspected to play a major role in the observed potential shifts. The pH-glass electrode is universally available, and that many enzymatic reactions produce pH changes may explain the vast amount of effort devoted to the construction of enzyme-based pH sensors. Potentiometric gas-sensing electrodes consist generally of a combination of pH-glass and reference electrodes and a gas-permeable membrane. A great diversity of procedures has been developed to fix enzymes or proteins on electrode supports. Potentiometric enzyme probes have been applied to the assay of a great variety of substances of clinical, biotechnological, and environmental interest.
