Electrochemical sensor research at the Laboratoire d'Electrochimie of the EPFL

This review presents some recent developments in the field of electroanalyt ical sensors. We first explain the working principle of electrochemistry at the interface between two immiscible electrolyte solutions (ITIES), illust rated by the example of copper transferring through a water/1,2-dichloroeth ane interface when the ionophore 1,4,7,10-tetrathiacyclododecane is present in the organic phase. The obtained results show that assisted ion-transfer reactions take place with both Cu-I and Cu-II, but that the interfacial pr ocess is complicated by the fact that Cut disproportionates in water and th at Cu-II can be reduced in the organic phase. Based on the same experimenta l methodology, a new type of amperometric detector for non-redox ions has b een developed using a composite polymer membrane supporting a gelified orga nic phase that can incorporate an ionophore such as valinomycin. We report here the use of a (o-nitrophenyl octyl ether)-(poy(vinyl chloride) (NPOE-PV C) gel micro-interface as a detector for cations and anions in ion-exchange chromatography. The main advantage of this approach is that selectivity an d sensitivity can be tailored by the choice of the ionophore and by the pol arisation potential. This ion detector has also been incorporated in a miniaturised total-analys is system (mu-TAS) fabricated in a polymer sheet by UV-laser photoablation. This microfabrication technique is used for the prototyping of a disposabl e capillary-electrophoresis microsystem comprising on-chip injector, separa tion column and electrochemical detector. This system is further used with built-in carbon-ink electrodes for the detection of electroactive species. These microsystems are now under development for immune-sensor applications .