Micromoulded polymer electrokinetic separation systems with variable volume sampling and integrated optical and conductivity detection.

The micromoulding of polymers has provided an ideal fabrication route for the construction of single-use integrated devices for elecrokinetic microseparations. Our designs have incorporated injector geometry that allows variable injection volumes in microchannels controlled by a combination of programmed hydrodynamics and electrophoresis. The utility of the injection scheme is demonstrated for isotachophoresis separations. Further developments have lead to the incorporation of parallel opposed conductivity detection electrodes in two ways. Firstly, by the injection of conducting polymer into a pre-moulded channel system and secondly through the moulding of the polymer microchannels around electrodes pre-moulded in conducting polymer (carbon fiber loaded nylon). This has provided a potential rapid manufacturing route for low cost polymer separation devices. As well as integrated conductivity detection electrodes, simple optical elements have been incorporated into injection moulded ITP devices to permit detection of the separated bands by optical means. A simple spherical lens was incorporated into the top section of the device which included the sample and buffer reservoirs. The lens was positioned directly above the conductivity detection electrodes, to permit simultaneous electrochemical and optical detection. The lens was used to perform visible absorption spectroscopy using an Ocean Optics spectrograph and tungsten-halogen fiber-optic white light source.