Electrophoretic separation of proteins on microchips

A mixture of model proteins was rapidly separated by capillary electrophoresis on a microfabricated device. The proteins were labeled with tetramethylrhodamine isothiocyanate and detected on-chip with laser-induced fluorescence. The small channel dimensions of the device allow the use of high ionic strength buffer to minimize protein adsorption to the channel walls. Electric field strengths as high as 600 V/cm could be applied without significant band distortion in 100 mM sodium phosphate buffer, and separations were completed within 60 seconds. The buffer pH was adjusted to optimize separation of proteins based on charge differences. A zwitterionic buffer additive, betaine, also reduced protein-wall interactions and improved the reproducibility of analyses. © 2000 John Wiley & Sons, Inc. J Micro Sep 12: 407–411, 2000