High-Speed Separations on a Microchip

Abstract

Fast, efficient separations are sought in liquid-phase analyses which incorporate a nondiscriminatory sample injection scheme and can implement a variety of detection modes. A glass microchip device for free solution electrophoresis was fabricated using standard photolithographic procedures and chemical wet etching. Separations were performed at several separation lengths from the injector to the detector with electric field strengths from 0.06 to 1.5 kV/cm. For a separation length of 0.9 mm, electrophoretic separations with baseline resolution are achieved in less than 150 ms with an electric field strength of 1.5 kV/cm and an efficiency of 1820 plates/s. For a separation length of 11.1 mm, a minimum plate height of 0.7 jtm and a maximum number of plates per second of 18 600 were achieved.Microfabricated chemical instruments show great promise for the laboratory and as advanced chemical sensors. Microfabrications of chemical separation techniques have received noticeable attention over the past several years and have included the techniques of gas chromatography,1 liquid chromatography,1 2 3456and capillary electrophoresis.3-7 Microelectronic devices have been able to achieve even faster response times in part due to miniaturization. Similar benefits may also accrue from miniaturization of some chemical measurement techniques. The response times of chemical measurements can often be an important issue, in particular in the case of chemical sensing.With microfabrication, the performance of many liquid separation techniques improves, especially capillary electrophoresis.8-10 For capillary electrophoresis, smaller column dimensions enable the power generated to be dissipated more efficiently, and as a direct result, separation devices can be operated at higher electric field strengths. The efficiency of the separations, therefore, improves in two areas. First, Joule heating, which leads to thermal gradients within the channel and ultimately contributes to the dispersion of the analyte

Inner ear drug delivery via a reciprocating perfusion system in the guinea pig

“…The ability to regulate flow and manipulate tiny quantities of fluids has already had a major impact on ink jet dispensers and laboratory analysis systems in the form "lab-on-a-chip" techniques and microarrays (e.g., [62][63][64]). The success of electrophoresis in microchannels for genomics has been a spectacular example [65]. Investigators have capitalized on continuing innovations in microfabrication to develop individual microfluidic components such as valves and pumps as well as diverse microsensors that operate in microchannels or microwells [57,58,[66][67][68][69][70][71][72][73][74][75][76][77] and several microscale active and passive flow regulators have been described [78][79][80][81].…”

Peer Reviewed: Shear-Driven Flow Approaches to LC and Macromolecular Separations

“…The injection process also must occur swiftly enough to prevent noninjected sample from leaking into the channel. In CE-and CEC-on-a-chip, the injection problem has occupied many researchers, who have had to make numerous adaptations to finally reach a suitable solution (17)(18)(19).…”

Shrinking the LC Landscape

“…Soon after, J. Michael Ramsey's group at Oak Ridge National Laboratory published its fundamental papers on µTAS (3,4), and the floodgates opened. What followed were reams of research papers on chip-based separations from laboratories around the world.…”