Effects of Injection Schemes and Column Geometry on the Performance of Microchip Electrophoresis Devices

A glass microchip column was fabricated for free-solution electrophoresis. The channels were wet chemically etched on a substrate using standard photolithographic techniques and were sealed using a direct bonding technique. Two methods of sample introduction are evaluated employing a cross-type channel geometry. With the preferred sample loading method, the volume of the sample plug can be accurately controlled and is time independent, enabling a constant volume to be injected. The injection can be controlled electronically and does not induce any electrophoretic mobility based bias. Separations were performed on a compact chip with a serpentine column geometry that has a 165-mm separation channel in an area of less than 10 mm × 10 mm. Band-broadening effects in a serpentine column pattern were studied.