A method to collect a plurality of target zones from a plurality of channels. The method includes introducing a plurality of compound mixtures into a plurality of microchannels on a microfabricated chip or a capillary tube. Optical signal measured at a detector window provides a signal of the position of a target zone. When a target zone has migrated to the location of a detector window, the detector senses an optical signal from the target zone and signals the system to disconnect a driving force from that channel. Once a plurality of zones in a plurality of channels are aligned, the driving force is reconnected and the zones are coeluted into a collection container.