Talking value and performance in Micro and Capillary LC chip, which allows easier replacement if the device becomes clogged or worn. This design provides several advanVeronikaR.Meyerreportsfromthe Second tages. Liquids filling an electrophoretic International Symposium on Miniaturized channel, for example, cannot leak out through the bores. Okumura also expects Total-Analysis Systems in Basel, Switzerland light guides to provide better optical properties, including low light scattering that Single-molecule can bring the laser emission directly to the best point of detection. DNA detection Although single-molecule DNA detection On another front, Olivier Guenat of the has been reported by several research University of Neuchatel (Switzerland) has groups in recent years, Carlo Effenhausshown that chip technology is not only er's group at Ciba (Switzerland) are the suitable for separation processes but also first to observe single molecules using a for nanoscale classical titration methods. CE separation channel on a microchip. Of special interest to Guenat's group are Effenhauser reports that the microchip coulometric methods because accurate device is simple and inexpensive to manu- results can be obtained because of the completeness of the chemical reaction facture. First, a silicon master wafer with and because numerous analytes in minute positive surface relief is constructed by volumes can be determined. standard wafer technology. From this master, polydimethylsiloxane negatives Guenat described a chip that carries a with channels can be easily cast, the nectotal of four electrodes (coulometric genessary reservoir holes for liquids erator counter, potentiometric indicator, punched, and combined with a flat sheet and reference electrodes) within a 200-nL of the same polydimethylsiloxane to form sample channel. Through the use of silver the chip. Adhesion is strong enough to electrodes, the precipitation titration of hermetically seal the electrophoresis chloride or the complexation titration of channels and reservoirs Effenhauser rethiosulfate is completed within 10 s; a deports. DNA is detected using a 488-nm ArH tection limit of 10"4 M KC1, which correlaser and in a 10-um x 20-um channel sponds to 10~9 g in 200 nL, was reporred. single dye-loaded DNA molecules could On the other hand, with platinum elecbe observed (one DNA molecule carries trodes the redox titration of Fe2+ with about 4800 dye molecules) Ce3+ can be achieved within 20 to 60 s depending on the analyte concentration Single-DNA molecule detection on a (10"~2 to 10"3 M) The standard deviation microchip also may have been achieved for all analyses is less than 1% Guenat by Johan Roeraade and co-workers from plans to reduce the 80-um channel height the Royal Institute of Technology in which should lead to shorter response Stockholm (Sweden), although this work times was too new to be confirmed before the symposium. Roeraade observed sharp electrophoretic peaks with no dispersion at all, which supports the single-molecule Analytical Chemists: hypothesis. His research group uses rectThe Next Generation angular electrophoretic channels (2-mm wide x 18-um high) on anisotropically Are you an analytical chemistry gradetched 15-nL nanovials on a chip, as well uate student who's planning to attend on glass tubes 50 longer with a Pittcon? If so, Analytical Chemistry cylindrical bore of 100-nm in diameter would like to discuss your experiNEWS FROM MICRO-TAS '96
Rethinking chip designs and purposes Optical detection on most chips is achieved using optical fibers mounted in special bores. Akihiko Okumura and coworkers at Hitachi (Japan) have gone a step further by microfabricating light guides on the chip. Optical fibers would then only be used at the exterior of the
ences as a graduate student over lunch. The information gathered from the group session will be used for a "Focus" article with a strict code of anonymity, so you don't need to worry about ramifications to yourself or to your advisor. For more information or if you are interested in participating, please contact Celia Henry by e-mail at
[email protected] or by telephone at 202-872-4372.
For around $6,000 you'll work with a system for Micro and Capillary LC that will let you achieve results like this:
Reproducibility (n = 8) Peak 1: 0.10% RSD, Peak 2: 0.05% RSD, Peak 3: 0.07% RSD The LC Packings Upgrade Kit for conventional HPLC systems — low or high pressure mixing — provides you with all components to achieve high reproducibility and high sensitivity separations in Micro, Capillary and Nano LC.
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