Design of enzyme electrode and their application?

THIS IS AN OVERVIEW OF ENZYME ELECTRODE:-

An enzyme electrode is the union of an enzyme, that biologic catalyst which acts sensitively and specifically with almost all organic and inorganic compounds in nature, with an

electronic sensor (an ion-selective electrode). The result is

an electrode that is useful for the assay of organic and inorganic compounds, in a manner as simple as a pH measurement with a glass electrode.

The principle of the enzyme electrode is simple: an enzyme is used which reacts with the compound to be assayed

either specifically or selectively. This enzyme, in an immobilized or insolubilized form, is placed onto a conventional ionselective electrode which measures either the decrease of one

of the reactants (i.e., O2 in the oxidation of uric acid or glucose) or a product (i.e., CO2 from an amino acid). The substance to be assayed diffuses into the layer of the enzyme in

the electrode, producing or consuming an electroactive substance; this is sensed by the base electrode. The potential or

current produced is a function of the concentration of the

substance assayed.

commercially available (or homemade) electrodes

have been used and can be used in construction of enzyme

electrodes: (1) glass electrodes-H+

and monovalent cation;

(2) gas-NH3, CO2)

and O2; (3) solid and "solid" liquid

membrane electrodes-NH4

, S~, CN~, and I"; and (4) Pt

electrodes.

Two basic techniques may be used in assay with enzyme

electrodes, kinetic and equilibrium. In the kinetic method,

the rate of change in the potential or current at the electrode

is measured, with the first 10-30 sec of response. This

change, AE or Ai/At, is then related to the content of substance to be assayed. In the equilibrium method, the steadystate current or potential, i or E, is measured and related to

the concentration. This relationship is logarithmic in the

case of potential (E) and linear in the case of current (i). The

rate method is faster and eliminates the possibility of error

due to side reactions that may consume the electroactive

substance.

Ans By-

MUSHARRAF ALI

CET-IILM-AHL

Gr. Noida