Fused-silica capillaries have been connected to microfluidic devices for capillary electrophoresis by drilling into the edge of the device using 200-μm tungsten carbide drills. The standard pointed drill bits create a hole with a conical-shaped bottom that leads to a geometric dead volume of 0.7 nL at the junction, and significant band broadening when used with 0.2-nL sample plugs. The plate numbers obtained on the fused-silica capillary connected to the chip were about 16-25% of the predicted numbers. The conical area was removed with a flat-tipped drill bit and the band broadening was substantially eliminated (on average 98% of the predicted plate numbers were observed). All measurements were made while the device was operating with an electrospray from the end of the capillary. The effective dead volume of the flat-bottom connection is minimal and allows microfluidic devices to be connected to a wide variety of external detectors.

No abstract

Clinical interest in the use of capillary electrophoresis (CE) has recently been extended to the microchip environment. Clinical analyses demand careful handling of complex samples that are often limited in quantity and in concentration. The integrated sample handling and analysis capabilities of microchip substrates thus seem ideally suited to clinical applications. This review surveys the development of sample handling (injection, mixing, and reaction) and separation elements on-chip. The integration of these elements to create a variety of clinical analyzers has been demonstrated. The application of microchip CE systems to human serum protein analysis, immunoassay, and DNA studies is reviewed, along with various other clinical applications. In addition, the clinical potential of the lab-on-a-chip concept is discussed.

No abstract