Amperometric electrode oxygen

Optical sensor Amperometric sensor Amperometric sensor Oxygen electrode/polysulfone membrane Platinum electrode Glassy carbon electrode/ methylene blue mediator Three separate enzyme electrodes of pH electrode/cellulose acetate membrane Platinum electrode... 

Such amperometric electrodes as the oxygen electrode are also frequently employed in enzymatic analyses involving consumption or release of oxygen... 

Fig. 12.15 A Clark-type electrode for amperometric dissolved oxygen measurement, (see also Clark, L. C., Wolf, R., Granger, D. and Taylor, Z. (1953) J. Appl. Physiol, 6, 189.)...

Inteiference with the reactants — An error in the measurement may arise if a compound reacts with a cosubstrate or a reaction product For example, ascorbic acid reacts with oxygen and interferes with the determination of glucose by an amperometric electrode that measures the reduction in the partial pressure of oxygen. This interference is lower when a peroxide-sensitive transducer is used, since this detects the production of H2O2. 

An example of amperometric methods used for analytical purposes is the sensor proposed in 1953 by Leland C. Clark, Jr. for determining the concentration of dissolved molecular oxygen in aqueous solutions (chiefly biological fluids). A schematic of the sensor is shown in Fig. 23.1. A cylindrical cap (1) houses the platinum or other indicator electrode (2), the cylindrical auxiliary electrode (3), and an electrolyte (e.g., KCl) solution (4). The internal solution is separated by the polymer... 

Almost all of the methods described in Chapter 23 can be used for in vivo analyses, both voltammetric and potentiometric ones. The former are used primarily in the analysis of organic substances, which, within certain ranges of potential, can be either oxidized or reduced. Another popular method is the amperometric determination of oxygen in different biological media with the Clark electrode (Section 23.3). 

Catalase has also been used as an enzyme label in competitive heterogeneous enzyme immunoassays. Catalase generates oxygen from hydrogen peroxide with the oxygen determined amperometrically with an oxygen electrode. This approach has been demonstrated for a-fetoprotein theophylline and human serum albumin... 

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