Miniaturized isotachophoresis in single-use integrated polymer substrates

Isotachophoresis is an electrokinetic separation technique in which a sample volume is placed between two electrolytes. The resulting separation consists of contiguous zones of constant composition whose length is proportional to component concentration in the sample. This paper describes the development of miniaturized formats consisting of microchannel structures fabricated in polymer substrates. Wells for electrolytes and sample are integrated with electrodes to permit activation of the separation process and setting up of the initial sample volume by electrophoresis. Detection is by conductivity and therefore universal for the monitoring of the separated zones due to the ions in the sample. Detector electrodes have been integrated into the separation channel and circuits developed to allow simultaneous detection in the presence of separation electric fields. The fabrication techniques reported are casting, dry-film lamination and microinjection moulding. Results presented illustrate the potential performance of devices with channel lengths of no more than a few cm. Studies of the detection electrode geometry have shown the need to minimize the detector length in order to maintain sharp inter-zone transitions. A modification to accommodate two-dimensional separations is discussed in the light of the performance of the single channel devices presented in this work. The objective of fabricating in polymer is to develop sufficiently low cost devices to allow economic single-use.