Isotachophoretic analysis using injection-moulded polystyrene chip devices

A new type of miniaturized separation chip for performing isotachophoresis has been produced. The design uses polystyrene as a substrate material and incorporates carbon fibre loaded polystyrene drive and conductivity detection electrodes. This fully polymeric composition allows for the devices to be produced using injection moulding. Ultrasonic welding is used for sealing to give robust chips that can potentially be easily transported and used outside of a laboratory environment. A batch of devices was produced and tested with a number of inorganic cationic species as samples. The entire batch of 22 devices were successfully used for isotachophoretic separations. Good reproducibility was observed in the qualitative behaviour of the devices. For example, with lithium a relative step height +/- standard deviation of 1.49 +/- 0.01 was observed on a run-to-run basis with a single chip and of 1.47 +/- 0.03 on a chip-to-chip basis over the entire batch of devices.