Clark oxygen electrode

Originally, a Clark oxygen electrode was used to measure a reduction in current due to the consumption of oxygen. Anodic detection of the hydrogen peroxide by oxidation at a platinum or carbon electrode was then introduced but, owing to the high electrode potential required, suffered from interference from other electroactive compounds in the sample. 

Oxygen uptake during substrate oxidation was measured with a Clark oxygen electrode (Rank Brothers, Cambridge, U.K.) at room temperature with 1 mM substrate in 0.25 mM sodium tartrate buffer, pH 3.0 (3 mL). Rates are expressed relative to veratryl alcohol oxidation. 

Fig. 3.8.2 Standard polarographic device with a Clark oxygen electrode...

Clark oxygen electrode. [D. t. Sawyer, A. Sobkowiak, and J. L. Roberts, Jr., Electrochemistry for Chemists, 2nd eel. (New York Wiley. 1995).] A modern, commercial oxygen electrode is a three-electrode design with a Au cathode, a Ag anode, a Ag I AgBr reference electrode, and a 50-(im-thick fluorinated ethylene-propylene polymer membrane. Leland Clark, who invented the Clark oxygen electrode, also invented the glucose monitor and the heart-lung machine. 

Clarke-Othmer process Clark oxygen electrode Clary sage oil [8016-63-5] Class A direct dyes Classification of dyes Classified removal Classifiers Clathrate... 

A major advance in the performance of amperometric oxygen sensors has been achieved by placing both the cathode and the anode behind the oxygen-permeable membrane (Fig. 7.4). This sensor is known as the Clark oxygen electrode. 

Fig. 7.4 Clark oxygen electrode (adapted from Fatt, 1976)...

The greatest impact of the Clark oxygen electrodes has been in medicine and physiology. (A schematic diagram of a catheter-size Clark electrode is shown in Fig. 7.7.) On the other hand, a temperature- and pressure-compensated Clark electrode for oceanographic measurements up to 600 ft has also been developed (Fatt, 1976). The normal temperature coefficient of the Clark electrode is 2%/°C... 

The respiratory activity of the brain tissue was determined by measuring the rate of oxygen uptake with a Clark oxygen electrode (7). The sample of tissue (a brain half) was treated exactly as if used in a calcium efflux experiment except no radioactivity or RF power was used. Following this procedure which required about 55 minutes, the tissue was placed in the oxygen electrode cell containing 1.6 ml of the standard medium (pH 7.8) at 37°C and the rate of oxygen uptake was recorded. 

Acetylcholineesterase and choline oxidase Sensors were developed consisting of a Clarke oxygen electrode modified by superposition (over the polypropylene membrane of the electrode) of a dialysis membrane on which AChE and ChO were immobilized. Both formats are based on the conversion of the substrate to choline which is oxidized in the presence of choline oxidase causing a reduction in p02 which is detected by the electrode. Free choline is measured with a similar electrode with only choline oxidase immobilized on the membrane. Calibration graphs were rectilinear upto 90 pM choline and upto 120 pM acetylcholine. Results were presented for the analysis of tissue extracts and pharmaceutical formulations. [115]... 

Enzyme electrodes play a vital role in the operation of - biosensor and -> biofuel cells. The term enzyme electrode was coined by Clark and Lyons after their first demonstration of a -> glucose sensor in which glucose oxidase was entrapped at a - Clark oxygen electrode using a dialysis membrane. The decrease in measured oxygen concentration was proportional to the glucose concentration. 

In the pioneer work of Updike and Hicks (40), the enzyme glucose oxidase (GOD) was maintained in a layer of acrylamide gel over a polarographic oxy n electrode (actually the Clark oxygen electrode). The current output of this probe results from the reduction of oxygen at a platinum electrode and thus is a function of the oxj n tension. When oxygen is not rate limiting and the glucose concentration is below the apparent for the immobilized GOD, there... 

Figure 1-10. Clark oxygen electrode and sample chamber assembly.

Biosensors based on a Clark oxygen electrode, coupled to tyrosinase immobilized by three different methods, were investigated for the determination of phenol in real matrices, such as water of various natural sources, industrial wastes and oil press. The feasibility study included direct use of the biosensors and in situ analysis. An integrated system, incorporating SPE, desorption, fractionation and biosensor detection, was validated for screening phenolic compounds in water. Two types of electrode were tested, solid graphite and CPE incorporating tyrosinase. Correct analyses were found for river water samples spiked with phenol (10 p.gL ), p-cresol (25 p.gL ) and catechol (1 A mul-... 

Quinoprotein glucose dehydrogenase and recombinant tyrosinase from Streptomyces antibioticus were immobilized on polyvinyl alcohol and coupled to a Clark oxygen electrode. LOD was 5 nM for dopamine (10a), L-dopa (10b) and adrenaline (epinefrine, 15a). An electroimmunological biosensor for p-cresol was developed, based on the... 

Clark oxygen electrode 977, 979 Claycop, use in nitration 633 Cluster formation 929 Clustering energies, gas-phase 224 CMPO derivatives 1406 Co-antioxidants 892 Cobalt-amine complexes, as oxidation catalysts 1199, 1201, 1205, 1206, 1209, 1211... 

Probably the most important developments in amperometric sensors were the Clark oxygen electrode and the amperometric glucose sensor. The latter is the most successful example of an enzyme-based sensor. 

We note here that the widely employed Clark oxygen electrode differs fundamentally from these devices (18, 63). The Clark device is similar in construction to the apparatus of Figure 2.4.5, in that a polymer membrane traps an electrolyte against a sensing surface. However, the sensor is a platinum electrode, and the analytical signal is the steady-state current flow due to the faradaic reduction of molecular oxygen. 

In this section the basic design and operation of these types of sensors are described. Examples of such sensors in common use are the Clark oxygen electrode [10] and the Severinghaus carbon dioxide electrode [11]. 

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