Microanalytic devices

Implementation of microanalytical devices presents some issues mostly related to the scale of the volumes. In fact, successive reduction in the sample volume may compromise analysis either because the measurement limit of the analytical method is exceeded or because the sample is no longer representative of the bulk specimen. Another drawback for microchip devices is microvolume evaporation of both sample and reagent from the microchip, compromising quantitative determination or inducing unwanted hydrodynamic flows. This problem has been addressed by designing pipetting systems that automatically replace fluid lost by evaporation or by enclosing the chip in a controlled... 

A good example for a microanalytical device is the gas sensor array. The conductometric approach for gas sensing was favored during the last years using metal oxides or conductive polymers. Unfortunately such sensors are quite unspecific and therefore sensor arrays with modified sensing layers have to be used. The selectivity derives from a sophisticated data processing using neural networks. Complete gas analysis systems with microfluidic and data acquisition are now under development. 

It can be concluded that although extensive research work has been done on microanalytical devices the enthusiasm and high expectations in such systems have not been fulfilled to date. Further work and technological breakthroughs are still necessary in the long run. Up to now only niche markets can be covered by microanalytical sensor systems for remote locations. 

This method combines the advantages of microfluidic real-time analysis with the cost-effectiveness of microanalytical devices. In contrast with the monolayer array confined to a microtiter-plate, it prevents problems such as solvent evaporation during the monolayer formation. Furthermore, it reduces dramatically the occupied space and the amount of reagents, enhances the automation of the fabrication process, and allows for continuous monitoring of analyte solutions. Regeneration of the channel activity for the sequential testing of multiple analytes is also possible. 

Ma ilflcatlon is dictated by the resolution of his measuring device which, for a scanned microanalytical device is 0.2mm or what his eye can observe on a CRT in the diffraction limit. 

Peterson, D. S., Rohr, T., Svec, R, and Frechet, J. M. J., Dual-function microanalytical device by in situ photolithographic grafting of porous polymer monolith Integrating solid-phase extraction and enzymatic digestion for peptide mass mapping. Analytical Chemistry, 75,5328-5335, 2003. 

Surface modification of poly(methyl methacrylate) used in the fabrication of microanalytical devices. Anal Chem 72(21) 5331-5337 9. Lahann J, Choi IS, Lee J, Jensen KF, Langer R (2001) A new method toward microengineered surfaces based on reactive coating. Angew Chem Int Ed 40(17) 3166-3169... 

Wei SY, Vaidya B, Patel AB, Soper SA, Me Carley RL (2005) Photochemically patterned poly(methyl methacrylate) surfaces used in the fabrication of microanalytic devices. J Phys Chem B 109 16988-16996... 

The low throughput, currently the major drawback of all scanning probe techniques, may be increased when SECM detection principles are used with multiple probes [189] or combined with integrated microanalytical devices [128]. 

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