ABSTRACT
The organic molecule is made to undergo an enzyme-catalyzed reaction with either consumption or generation of an ion for which an ion-selective electrode is available. Enzyme electrodes permit measurement of organic molecules with the same facility that ion-selective electrodes permit the measurement of ions. The use of an enzyme as the catalyst permits reactions to take place under mild conditions of temperature and pH and at very low substrate concentration. The response characteristics of enzyme electrodes are subject to many variables in their design and construction, and an understanding of the theoretical basis of their function would help to improve their performance. Enzyme electrodes for determining amino acid concentrations were first used by G. G. Guilbault and E. Hrabankova. The enzyme creatininase has been employed in the construction of an electrode for creatinine. The enzyme was present in a liquid membrane held around the sensor surface of an Orion ammonia gas-sensing electrode.
