On-chip quantitative PCR using integrated real-time detection by capillary electrophoresis.

Quantitative PCR (qPCR) has been widely used for the detection and monitoring of a variety of infectious diseases. PCR and CE were integrated into a microfluidic chip that was designed to achieve rapid real-time amplicon sampling, separation, and quantitation without requiring various probes. A novel chip design allows the overlapped execution of PCR and CE, minimizing the time required for CE analysis after each PCR cycle.

Controlling data quality and reproducibility of a high-sensitivity immunoassay using isotachophoresis in a microchip.

This report describes a method of controlling the sensitivity and reproducibility of a microchip-based immunoassay by using isotachophoresis to preconcentrate the antigen and antibody prior to binding. Gel electrophoresis separation is coupled to the preconcentration step to separate the immunocomplex products formed. The system employs a quartz-based LabChip that automates the metering, preconcentration, reaction, separation, and detection.

Sample stacking revisited: a personal perspective.

One of the major challenges in capillary electrophoresis and other miniaturization separation techniques is to maintain high detection sensitivity in the increasingly smaller dimension. Numerous on-column sample preconcentrating procedures, based either on electrokinetic focusing or chromatographic effects, have been developed. This review will discuss some practical approaches to sample stacking from a personal perspective.

Increase of separation resolution through field enhancement in microchips.

An enhanced ability to separate charged species from neutral compounds in a microfluidic chip is demonstrated using a chip design with low-resistance electrode channels operating with a multiport pressure/voltage controller. A factor of 2.7 improvement in resolution was obtained from chips made using identical mask designs but different etch depth protocols.

Selective ion extraction: a separation method for microfluidic devices.

A separation concept, selective ion extraction (SIE), is proposed on the basis of the combination of hydrodynamic and electrokinetic flow controls in microfluidic devices. Using a control system with multiple pressure and voltage sources, the hydrodynamic flow and electric field in any section of the microfluidic network can be set to desired values. Mixtures of compounds sent into a T-junction on a chip can be completely separated into different channels on the basis of their electrophoretic mobilities.

Electroosmotic pumping in microchips with nonhomogeneous distribution of electrolytes.

A general equation to calculate the node pressure at a junction in a microfluidic network is presented. The node pressure is generated from both the hydrodynamic flow due to the external applied hydraulic pressures and the electrokinetic flow resulted from the applied electric field. Pure electroosmotic flow has a plug-flow profile and pressure flow has a parabolic flow profile.