High-speed analysis of proteins by microchip isoelectric focusing with linear-imaging UV detection.

High-speed analyses of proteins by microchip isoelectric focusing (MCIEF) were investigated on straight channel chips. By employing a commercially available microchip electrophoresis instrument equipped with a linear-imaging UV detector, sample proteins focused in a separation channel could be detected without a mobilization step. Typically, standard proteins were focused within 210 s at different positions in a separation channel with its total length of 38.8 mm on the basis of their pI values. The linear relationship between the focused position of each protein and its pI value was observed in the pH range from 6 to 10. The formation process of a pH gradient in the microchannel and the effects of the applied voltage and the channel length on the MCIEF separation were also investigated.