Membrane-covered amperometric oxygen

The limiting current obtained at a membrane-covered amperometric device is a function of time, reaching in due course a steady-state value. The current-time transient cannot be described by a single equation, because different transport mechanisms operate during this time interval. For a typical membrane-covered amperometric oxygen detector with an electro-... 

For the stationary registration, long-term stability of the sensor or analytical unit is the dominant criterion, while moving sensors have to be optimized for minimum response times. For example, the fast response time of membrane covered amperometric oxygen sensors and long-term stability are mutually exclusive. The sensors can only be optimized for one or the other criterion. 

While most gas sensors rely on potentiometric detection, the important oxygen probe is based on amperometric measurements. In particular, membrane-covered oxygen probes based on the design of Clark et al. (105) have found acceptance for many applications. The sensor is based on a pair of electrodes immersed in an electrolyte solution and separated from the test solution by a gas-permeable hydrophobic membrane (Fig. 6.22). The membrane is usually... 

According to this equation, for an amperometric oxygen-sensing electrode covered by a membrane of 100 pm thickness the steady-state current will be attained 38 s after changing the oxygen concentration (D = 3.9 10 cm Vs). Half of the steady-state value is reached at... 

The first biosensor was reported in 1962 [131, 132], and consisted of glucose oxidase bound to a membrane covering an amperometric oxygen electrode. This was the first device that could be used to measure the concentration of an enzyme substrate without adding enzyme as a reagent to the analyte solution. 

Miniaturized amperometric sensors have been prepared also in thick-film and thin-film techniques [25]. As an example, in Fig. 8 the layout of a planar amperometric oxygen sensor in thin-film technique is shown. The KCl electrolyte and PUR membrane layers covering the electrode system are applied by dispenser technique. 

Nearly all sensors used for in situ registration of dissolved oxygen in seawater are of the amperometric membrane covered electrode type introduced by Clark et al. (1953). A de-... 

There are also nongalvanic oxygen sensors that are based on the same principles. This type of oxygen sensor typically consists of an inert metallic cathode covered with a gas-permeable membrane and a silver anode. These sensors are usually connected in series with a 1.5 V battery and an external potential of 0.8 V is applied between the electrodes to initiate the amperometric measurement of oxygen. One such sensor employs a gold cathode, a silver anode, and a potassium chloride gel as the electrolyte. 

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. ... 

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