Sensor systems chemical composition analyzers

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. 

The concentrations of the different members of a DCL depend on the physical and chemical environment of the respective system (pH, solvent, concentration of target molecules, etc.). The Ubrary composition is therefore a characteristic feature of the respective environment If the DCL composition can be transduced into a signal output, it is possible to use the DCL as a sensor. Typically, DCLs are analyzed by nuclear magnetic resonance spectroscopy or high-performance hquid chromatography. For sensing purposes, however, faster and cheaper analysis methods such as fluorescence or ultraviolet-visible (UV-Vis) spectroscopy are preferred. These techniques can be used if the DCL is composed of compounds with different color or fluorescence properties (Figure 7.1). 

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