Membrane-covered amperometric devices

An important consequence of this equation is that the limiting current is a function of the permeability of the membrane. Unfortunately, membrane properties such as permeability are a function of time and ambient conditions, particularly temperature. Accordingly, there are advantages to operating membrane-covered detectors away from this steady-state condition. For the typical detector, the limiting current at times less than 100 ms from the imposition of the measurement potential pulse is given by 

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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-... 

Placing an amperometric device in real samples, e.g. blood, a degradation of electrochemical performance over time occurs due to contamination of the electrode reducing electro chemically accessible reaction sites [67]. Therefore surface modifications or special electrode materials like e.g. carbon are needed and the electrodes have to be covered with functional membranes to ensure full faradaic current. This poses a problem in the production even using special technologies. 

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. 

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