SPE sensors also have a stronger dependence of the signal on the

SPE sensors also have a stronger dependence of the signal on the gas flow rate [1,14] and are therefore usually used in systems with a forced and constant gas flow.The electrolyte phase carries the cell current by enabling the transport of charge carriers in the form of ions and often provides co-reactants to electrode and allows the removal selleckchem of ionic products from the reaction site. Note, that counter and reference electrodes may be combined into a single electrode [1,5]. Each sensor can have a unique design and a different set of materials and geometries for membranes, electrolytes, and electrodes in order to take advantage of chemical properties of a specific target analyte and survive under various operating conditions [5].A critical issue in design of amperometric sensors is achieving selectivity, i.

e., situation that the sensor current depends on analyte concentration but is insensitive towards possible interferents in the solution. In early amperometric measurements selectivity was achieved by the choice of working electrode material and the potential of the working Inhibitors,Modulators,Libraries electrode.A major breakthrough in this field was achieved in 1953, when Leland C. Clark developed the practically usable membrane oxygen sensor for measuring oxygen tension in the cardiovascular system in vitro and in vivo [18]. The choice of membrane material became the third important tool for achieving selectivity. With this advancement actually the amperometric sensors were born. After patenting the method in 1959, electrochemical membrane covered amperometric sensors have become a common method in situ measurement of oxygen and the design is often called ��Clark type��.

By appropriate selection of the membrane material (PTFE, PFA, FEP, PE, PP, silicone, cellophane Inhibitors,Modulators,Libraries etc.) and specific properties, one can control the analytical characteristics of the sensor, permitting the analysis of several analytes over a wide range of concentration [5]. Modern Clark electrodes are often fitted Inhibitors,Modulators,Libraries with a porous PTFE membrane. Because of the hydrophobicity of the material, the pores are not wetted by the aqueous solution and are impermeable for ions and polar organic compounds but allow the transport of dissolved non-polar gases to the electrode [1]. Out of the gases normally dissolved in the aqueous environment only oxygen can undergo reduction at the working electrode.

This way the selectivity of the dissolved oxygen sensor is ensured. Several diffusion layers are formed in the classic Clark sensor: the electrolyte layer, the membrane and a stagnant layer [5,14]. The thinner are the layers the higher the sensitivity and the faster the Inhibitors,Modulators,Libraries response.The electrolyte can be an aqueous Carfilzomib or a non-aqueous solution or a so-called solid-phase electrolyte www.selleckchem.com/products/17-AAG(Geldanamycin).html (SPE), which in most cases is a conductive polymer. These are good because of their high boiling point and often very high ionic conductivity.

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