Oxygen amperometric

There are a number of possible inhibitors in the glucose determination. Most of them, however, occur in tlie second enzymatic reaction. The glucose oxidase method would be more specific, then, if the hydrogen peroxide were measured directly without the need for a second enzyme. For example, added iodide ion, in the presence of a molybdenum(VI) catalyst, is rapidly oxidized to iodine. The iodine concentration can be followed amperometrically (Chapter 15). An alternative is to measure the depletion of oxygen amperometrically. 

Damos FS, Luz RC, Tanaka AA, Kubota LT (2010) Dissolved oxygen amperometric sensor based on layer-by-layer assembly using host-guest supramolecular interactions. Anal Chim Acta 664(2) 144-150... 

The choline electrode usually consists of an amperometric transducer and immobilized choline oxidase. The most frequently used electrochemical transducers are hydrogen peroxide electrodes (26-28,33-36). The amperometric signal in this case is due to electrooxidation of hydrogen peroxide, which is the co-product of the enzymatic choline oxidation (equation 2). Oxygen amperometric sensors (Qark-type electrodes) have been also used as basic transducers for choline electrode construction (29, 32, 37). The signal in this case is based on the reduction of molecular oxygen which is the co-reactant in reaction (equation 2). Redox mediators hexacyanoferrate (26), ferrocene derivatives (38) and tetracyanoquinodimethane (39) have also been used in the construction of choline electrodes. 

Amperometric gas sensors are the second most important group of electrochemical gas sensors. The development of these sensors can be traced back to the introduction of the Clark-electrode in the mid-1950s, which is well known for the determination of dissolved oxygen. Amperometric gas sensors consist of a working electrode mostly covered by a membrane, a counter and a reference electrode which are in connection with a liquid electrolyte solution. These sensors have been designed in different forms and are significant also in commercial terms. The schematic setup is shown in Fig. 19.5. ... 

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... 

Household appliances can also benefit from improvements in other areas. For example, oxygen sensors that measure the 02-concentations in exhaust gas have been developed that combine a Nernst type lambda gauge (which can measure only the ( -concentration at one lambda-point) with an amperometric 02-pumping cell. 

Diffusion Currents. Half-wave Potentials. Characteristics of the DME. Quantitative Analysis. Modes of Operation Used in Polarography. The Dissolved Oxygen Electrode and Biochemical Enzyme Sensors. Amperometric Titrations. Applications of Polarography and Amperometric Titrations. 

Fig. 1. Amperometric monitoring of the autoxidation of epigallocatechin gallete in the presence of (A) 0, (B) 2.0, (C) 5.0, (D) 10, (E) 20, and (F) 50 pm CuCl2. The measurements were performed in 0.1 M Tris buffer (pH 9.0) with a Clark type oxygen electrode at 28 °C. The epigallocatechin gallate concentration was fixed at 50 pm. The catechin stock solution was injected into the test solution at t = 0. The inset shows the (initial) steady-state autoxidation rate as a function of Cu2+ concentration. Reprinted from Biochimica et Biophysica Acta, vol. 1569, Mochizuki, M. Yamazaki, S. Kano, K. Ikeda,T., Kinetic analysis and mechanistic aspects of autoxidation of catechins, p. 35, Copyright (2002), with permission from Elsevier Science.

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