Microchip chemistry

Kim, H.B., Hagino, T., Sasaki, N., Kitamori, T., Ultrasensitive detection of electrochemical reactions by thermal lens microscopy for microchip chemistry. Micro Total Analysis Systems 2003, Proceedings 7th flTAS 2003 Symposium, Squaw Valley, CA, Oct. 5-9, 2003, 817-820. 

Kitamori, T., Tokeshi, M., Hibara, A. and Sato, K., Thermal lens microscope and microchip chemistry. Anal. Chem., 76,52A, 2004. 

Kitamori T, Tokeshi M, Sato K, Hibara A (2004) Thermal lens microscopy and microchip chemistry. Anal Chem 76 52A... 

A technique of microchip chemistry was introduced into an on-line solvent extraction system for the future study of superheavy elements by Ooe et al. [137]. Microchips made of glass plates have microscale ditches of typically 1-100 pm in width and depth. Because of a large specific interfacial area and a short diffusion length of solutes, chemical equilibria are rapidly achieved in the microspace, which is suited to the chemical separation of short-lived nuclides. On-line solvent... 

Capillary electrophoretic separations are performed in small diameter tubes, made of Teflon, polyethylene, and other materials. The most frequently used material is fused silica. Fused silica capillaries are relatively inexpensive and are available in different internal and external diameters. An important advantage of a fused silica capillary is that the inner surface can be modified easily by either chemical or physical means. The chemistry of the silica surface is well established due to the popularity of silica surfaces in gas chromatography (GC) and liquid chromatography (LC). In capillary electrophoresis, the silica surface is responsible for the EOF. Using surface modification techniques, the zeta potential and correspondingly the EOF can be varied or eliminated. Column fabrication has been done on microchips.13... 

Solid-supported technologies are already well established methods in medicinal chemistry and automated synthesis. Over the last couple of years new trends have evolved in this field which are of utmost importance as they have the potential to revolutionize the way chemical synthesis especially for library production is performed. Microchip-based synthesis technologies and multistep sequences with solid-supported catalysts or reagents in flow-through systems are only two spectacular examples. A new approach is the use of solid-supported systems for the scale-up of chemical reactions thereby enabling the rapid and smooth transition from discovery to development units. 

Among the various possibilities that offer the EC detection, ampe-rometry and conductimetry are, in this order, the most common. Although potentiometry results are a very interesting technique in many fields of Analytical Chemistry, it has not found enough echo in the microchip technology. Its incursion in microchips is related with the employment of ion-selective electrodes for Ba2+ determination [55] or potentiometric titration of iron ferrocyanide [56], but it has not yet been associated with CE microchips. 

Microfluidics and miniaturization hold great promise in terms of sample throughput advantages [100]. Miniaturization of analytical processes into microchip platforms designed for micro total analytical systems (/i-TASs) is a new and rapidly developing field. For SPE, Yu et al. [123] developed a microfabricated analytical microchip device that uses a porous monolith sorbent with two different surface chemistries. The monolithic porous polymer was prepared by in situ photoinitiated polymerization within the channels of the microfluidic device and used for on-chip SPE. The sorbent was prepared to have both hydrophobic and ionizable surface chemistries. Use of the device for sorption and desorption of various analytes was demonstrated [123]. 

FIGURE 4.12 Schematic drawings of CE chips with added microelectrodes to achieve the pinching effect (a) the conventional cross type CE microchip, (b) two Au electrodes of equal lengths were added (x = y = 0.5 mm) [562]. Reprinted with permission from the Royal Society of Chemistry. 

Henry, C. Micro Meets Macro interfacing microchips and mass spectrometers. Analytical Chemistry News and Features, 69, 359A-361A. 

For many chemical processing applications, microchemical systems should include solvent extraction and interfacial reaction components utilizing both aqueous and organic (or gas and liquid) solutions. Both solutions must be controlled to realize general chemistry in a microchip. In 1990s, electroosmotic flow was used in microchip electrophoresis (Auroux et al., 2002 Reyes et al., 2002) however, the electroosmotic flow is restricted to the flow control of only one type solution (aqueous buffer). Therefore, electroosmotic flow is not suitable for a flow-control method to... 

The Nervous Systems Research branch of Novartis Pharma Ltd in Basel, Switzerland, carried out the aldol reaction using a microchip reador under eledroosmotic flow conditions. Aldol reactions are well-established routes for C—C bond formation in organic chemistry. 

In this, the concluding chapter of our journey through the history of chemistry, we shall look at topics where chemical methods or ideas have proved useful, but not worry further about drawing a line around the science. Nor shall we worry about drawing a line between pure and applied science. Many industries employ chemists to do pure research, in the reasonable expectation that some of it will prove useful. Most chemists are employed in applied science that is the aspect of chemistry that has had the greatest effect on our environment and on us. In the past one hundred and fifty years, chemical synthesis has become ever more powerful, and it is fair to say that chemistry is the only science that now builds or creates much of what it goes on to study, from artificial elements to the latest plastics and the most powerful pharmaceutical chemicals, from fertilizers to microchips. Chemists have been enormously successful in their explorations, and the results of their work have transformed the world in which we live and work. 

Armstrong RW, Brown SD, Keating TA, Tempest PA, Combinatorial synthesis exploiting multiple-component condensations, microchip encoding and resin capture, in Combinatorial Chemistry Synthesis and Application (Eds. Wilson SR, Czarnik AW), pp. 153-190, 1997, John Wiley Sons, New York. 

Molecules interact with the surfaces of solids in almost every environment in the universe. In addition to purely intellectual interest, we customarily justify studying these interactions on technological grounds, heterogeneous catalysis and the fabrication of microchips being the most frequently listed applications. However the field is much more broadly relevant the adsorption and desorption of atoms and molecules on the surfaces of dust grains is very important to molecule formation in the interstellar medium, reactions on the surfaces of ice crystals is important in atmospheric chemistry and reactions at surfaces determine the behaviour of medical implants in our bodies. 

Principles and Applications in Analytical Chemistry and Microchip Technology... 

In traditional analytical chemistry the determination of enantiomeric purity is sometimes carried out by capillary electrophoresis (CE) in which the electrolyte contains chiral selectors such as cyclodextrin (CD) derivatives [54], Unfortunately the conventional form of this analytical technique allows only a few dozen ee determinations per day. However, as a consequence of the analytical demands arising from the Human Genome Project, CE has been revolutionized in recent years so that efficient techniques for instrumental miniaturization are now available, making ultra-high-through-put analysis of biomolecules possible for the first time [55]. Two different approaches have emerged, namely capillary array electrophoresis (CAE) [55a - e] and CE on microchips (also called CAE on chips) [55f - m[. Both techniques can be used to carry out... 

The synthesis of a model library of 100 amides from anhydrides on microchips has been described with quality control indicating excellent yields of pure amides and no cross-contamination of the wells (199). This test validated the chip structure, the seals of the system, and the electrohydrodynamic pumping system in the presence of solvents such as DMF and methanol and reagents such as the anhydrides, piperidine, and DIPEA. More challenging chemistries and larger libraries have also been presented. 

The technique of isoelectric focusing has proven to be a useful tool in protein chemistry, and this too has been adapted to the microchip. Using 7-cm-long channels in glass microchips (200 [Xm wide and 10p,m deep) mixtures of Cy5-labeled peptides can be focused in less than 30 seconds. This same procedure has also been applied to plastic microchips made from EMMA by laser ablation and shown to focus mixtures of peptides labeled with rhodaraine green. Results for this type of microchannel isoelectric focusing are available in less than 5 minutes compared with traditional techniques that take over 1 hour. 

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