Based on ion-pairing interactions, which are strongly reinforced upon oxidation to their ferrocenium form, (ferrocenylmethyl)trialkylammonium cations are able to electrochemically sense dihydrogenphosphate and ATP anions in organic electrolytes through two-wave voltammetric features, allowing their amperometric titration. The successful transfer of these electrochemical sensing properties from the homogeneous phase to an electrode surface was achieved using functionalized polypyrrole films synthesized by oxidative polymerization of pyrrole-containing (ferrocenylmethyl)trialkylammonium derivatives. (C) 2004 Elsevier Ltd. All rights reserved.