An amperometric sensor for non-electroactive ions was designed, evaluated in flow injection analysis, and applied as a novel detector in suppressed ion chromatography. It consists of a carbon paste electrode modified with either a polycationic or a polyanionic polymer containing a suitable charge transfer mediator (Fe(CN)63− or Cu2+), operating in an indirect amperometric mode. The detection mechanism involves ion exchange between the non-redox ionic analyte and the electroactive mediator, in the polymer particles located at the electrode surface, followed by the electrochemical transformation of the mediator species leached out of the polymer at the electrode ∣ solution interface. As detection was achieved in the absence of added supporting electrolyte, the amperometric signal contains both faradic and capacitive components. Optimisation was performed to get the highest faradic signals, by varying various experimental parameters (i.e. applied potential, composition of the electrode). These systems were then successfully applied to the analysis of mixtures of cations (Li+, Na+, K+, NH4+, Ca2+, Mg2+) and anions (F−, Cl−, NO2−, NO3−, SO42−, PO43−) subsequent to chromatographic separation. Good operational stability was observed, with typically less than 5% signal loss for 50 successive measurements.