Two-dimensional electrochromatography/capillary electrophoresis on a microchip

A two-dimensional separation system on a microfabricated device was demonst rated using open-channel electrochromatography as the first dimension and c apillary electrophoresis as the second dimension. The first dimension was o perated under isocratic conditions, and the effluent from the first dimensi on was repetitively injected into the second dimension every few seconds. A 25-cm separation channel with spiral geometry for open-channel electrochro matography was chemically modified with octadecylsilane and coupled to a 1. 2-cm straight separation channel for capillary electrophoresis. Fluorescent ly labeled products from tryptic digests of beta -casein were analyzed in 1 3 min with this system.