A two-dimensional separation system on a microfabricated device was demonstrated using open-channel electrochro-matography as the first dimension and capillary electrophoresis as the second dimension. The first dimension was operated under isocratic conditions, and the effluent from the first dimension was repetitively injected into the second dimension every few seconds. A 25-cm separation channel with spiral geometry for open-channel electro-chromatography was chemically modified with octadecyl-silane and coupled to a 1.2-cm straight separation channel for capillary electrophoresis. Fluorescently labeled products from tryptic digests of β-casein were analyzed in 13 min with this system.
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