Analyzers biochemical sensors

In the following, only chemical and biochemical sensors are considered They make use of specific "key-lock" interactions which convert chemical to electronic information Three different tasks are usually fulfilled by chemical sensors, i e the quantitative and selective determination of individual particles (such as molecules or ions in gases or liquids), the determination of gross parameters (such as toxicity), or the quantitative characterization of odors (such as smells monitored qualitatively by the human nose) These requirements can only be achieved with sensor systems which in the most general case contain ten components for analyzing gases or liquids [4]... 

Entrapment of biochemically reactive molecules into conductive polymer substrates is being used to develop electrochemical biosensors (212). This has proven especially useful for the incorporation of enzymes that retain their specific chemical reactivity. Electropolymerization of pyrrole in an aqueous solution containing glucose oxidase (GO) leads to a polypyrrole in which the GO enzyme is co-deposited with the polymer. These polymer-entrapped GO electrodes have been used as glucose sensors. A direct relationship is seen between the electrode response and the glucose concentration in the solution which was analyzed with a typical measurement taking between 20 to 40 s. 

Correlation between the results, obtained by using the known sensors and methods and the proposed sensors, is very good. The approach demonstrates perspectives for creating enzyme-free chemical/biochem-ical sensors. It also allows the elimination of disadvantages of enzyme-containing sensors, particularly, their time and thermal instability, high cost and necessity to use substrate in the analyzed solution. 

Significant advances have occurred during the past decade to miniaturize the size of the measurement system in order to make online analysis economically feasible and to reduce the time delays that often are present in analyzers. Recently, chemical sensors have been placed on microchips, even those requiring multiple physical, chemical, and biochemical steps (such as electrophoresis) in the analysis. This device has been called lab-on-a-chip. The measurements of chemical composition can be direct or indirect, the latter case referring to applications where some property of the process stream is measured (such as refractive index) and then related to composition of a particular component. 

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