Ionode detection and capillary electrophoresis integrated on a polymer micro-chip

A miniaturised capillary electrophoresis system integrating amperometric ionodes for the electrochemical (EC) detection of non-redox ionic species is presented. The micro-chip comprising an injection, a separation and an amperometric ion-sensitive detector structure has been developed on a single planar polymer substrate. UV excimer laser photoablation on a poly(ethylene terephthalate) (PET) substrate allows the fabrication of the complete micro-chip in a single step and in a very short time (less than 20 min). An electrokinetic separation procedure by means of a floating high voltage (HV) source is employed to improve the electrical decoupling between HV and EC detection. As a result, no significant distortion in the EC response is observed even for electrophoretic currents up to 140 μA. Also the floating HV prevents electrokinetic injection bias and the amount of the electrokinetically injected sample was found to be constant as a function of the injection duration. As a preliminary demonstration, a sample solution containing two non-redox organic ions can be analysed in less than a minute.