Clark sensor, oxygen

For completeness it should be mentioned that some of the theoretical conclusions for SECMIT are analogous to earlier treatments for the transient and steady-state response for a membrane-covered inlaid disk UME, which was investigated for the development of microscale Clark oxygen sensors [62-65]. An analytical solution for the steady-state diffusion-limited problem has also been proposed [66,67]. 

The decrease of oxygen reduction current measured with the Clark oxygen sensor indicates the concentration of glucose. 

Special electrochemical sensors that operate on the principle of the voltammetric cell have been developed to measure substrates such as oxygen and glucose. In the Clark oxygen sensor, a 1.5 V potential difference is applied between a silver anode and a platinum cathode which are both in contact with a KCl solution separated from the sample by a membrane permeable to oxygen (Fig. 19.6). 

While voltammetric/ainperometric techniques can be applied to detect a wide range of species, the selectivity offered for measurements in complex clinical samples— where many species can be electroactive—is rather limited. For example, as stated in the above discussion relevant to the Clark oxygen sensor, in the absence of the gas-permeable membrane, other species that can be reduced at or near the same Eappi as oxygen would cause significant interference. 

M The Clark oxygen sensor is widely used in clinical laboratories for the determination of dissolved O2 in blood and other body fluids. 

For a detailed discussion of the Clark oxygen sensor, see M. L. Hitchman. Mecsuyeinsfit of Dissolved Oxygen, Chapters 3-5. New York Wiley, 1978. 

Clark oxygen sensor A voltammetric sensor for dissolved oxygen. 

Fig. 8. Clark oxygen sensor. (1,2) contacts, (3) electrolyte, (4) reference anode (Ag/AgCl), (5) working cathode (Au or Pt), (6) gas-permeable membrane, (7) 0-ring.

There are two major sensors classes that use liquid electrolytes amperometric and poten-tiometric sensors. The earliest example of an amperometric gas sensor, the Clark oxygen sensor used for the measurement of oxygen in the blood is more than 40 years old. The amperometric sensor produces current signal, which is related to the concentration of the analyte by Faraday s law and the laws of mass transport. It is operated in a region where mass transport is limiting and therefore has a linear response with concentration of the analyte. This type of sensor has now been developed in many different geometries with different types of material coated or uncoated to enhance sensitivity and selectivity (Figure 15.5). 

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