Integrated detection system electrophoresis

K. M. Walsh, and R. S. Keynton, Fully Integrated On-Chip Electrochemical Detection for Capillary Electrophoresis in a Microfabricated Device, Anal. Chem. 2002, 74, 3690 M. L. Chabinyc, D. T. Chiu, J. C. McDonald, A. D. Strook, J. F. Christian, A. M. Karger, and G. M. Whitesides, An Integrated Fluorescence Detection System in Poly(dimethylsiloxane) for Microfluidic Applications, Anal. Chem 2001, 73, 4491. 

At present, there are advanced difference gel electrophoresis (DOGE) Systems and 2-D fluorescence difference gel electrophoresis (2-D DIGE) which enable the analyst to use simultaneously modern (more precise) methods of fluorescent analysis with 2-D electrophoresis (using internal patterns), aided by a fully integrated bioinformatics system. Such systems allow more complete differential protein analysis, while the application of internal standards eliminates differentiation between the intervals, thus ensuring that even the smallest differences will be detected irrespective of the multitude of components. This guarantees reproducibility of results and their statistical reliability. Such assays are one of the platforms employed in the research based on the proteomics method. 

In the past decade, microchip electrophoresis has undergone substantial development, including integrated microchip designs, advanced detection systems, and new applica-tions. In the clinical diagnostic arena, the main analytes of interest for extrapolation to the microchip platform are proteins and DNA. 

Chemical analysis systems, such as spectrophotometry, high-performance liquid chromatography, capillary electrophoresis and immunoassays, always consist of a combination of a reaction or separation and a detection system. In the following section, some generic features for chemical reactions and separations are addressed, and the major conventional detection techniques as well as the integration and miniaturization of optical components used in chemical analysis are briefly reviewed. In the key... 

Amperometry can be used in conjunction with capillary electrophoresis (CE). On chip the CE system uses an electric held for separation of analyte molecules in a narrow channel or capillary on the basis of electrophoretic mobilities of molecules. The CE system usually consists of a sample injection channel, a separation channel, and electrodes for application of electric held, as well as measurement of current signals. There are quite a few instances of such development [56-58]. For example, Wang et al. integrated micromachined capillary electrophoresis with amperometric detection for dopamine detection [59]. The glass chips consist of a separation channel, a sample injection channel, and a thin layer of sputtered An (acting as working electrode) at the outlet of the separahon channel (Fig. 5.11). Dopamine was delected with LOD of 1 pM and linear response from 20 to 200 pM. 

J. Lichtenberg, N.F. de Rooij and E. Verpoorte, A microchip electrophoresis system with integrated in-plane electrodes for contactless conductivity detection, Electrophoresis, 23 (2002) 3769-3780. 

Mogensen, K.B., Petersen, N., Htibner, J., Kutter, J., In-plane UV absorbance detection in silicon-based electrophoresis devices using monolithically integrated optical waveguides. Micro Total Analysis Systems, Proceedings 5th ytTAS Symposium, Monterey, CA, Oct. 21-25, 2001 Kluwer Academic Publishers, Dordrecht, the Netherlands, 2001, 280-282. 

Jemere, A.B., Oleschuk, R.D., Ouchen, F., Fajuyigbe, F., Harrison, D.J., An integrated solid-phase extraction system for sub-picomolar detection. Electrophoresis... 

Htaoka, Y., Notomi, T., Baba, Y., Integrated microsystem of isothermal amplification of DNA and electrophoresis on a microfabricated plastic chip for detection of specific gene and analysis of genetic materials. Micro Total Analysis Systems Proceedings pTAS 2002 Symposium, 6th Nara, Japan, Nov. 3-7, 2002, 215-216. 

A unique micro integration methodology has been shown for a wide variety of chemical systems. The methodology comprises MUOs, CFCP, and TLM. Some of its applications, which were hardly realized with conventional microsystems based on electrophoresis and LIF detection, were explained with examples. All these examples proved that micro chemical systems drastically reduce chemical processing time and improves efficiency. The micro chemical systems are concluded to be promising as flexible, smart, and mobile advanced chemical systems in near-future chemical technology. 

Figure 4-33. Block diagram of capillary electro- carried out close to the cathode in a region phoresis equipment. Capillary electrophoresis where the capillary is transparent, allowing equipment consists of a thermostatted capillary photometric or fluorimetric analysis of the whose ends are placed in the electrode buffer eluate. The detector system is linked either to a chambers these contain the electrodes attached recorder/integrator or to a PC. to a high-voltage power supply. Detection is...

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