Polypyrrole (PPy) and overoxidized polypyrrole (OPPy) films were used as a potentiometric detector in ion chromatography, in order to determine some anions and cations in water samples. Electrodeposition of PPy film was performed by constant potential at +0.80V (vs. Ag/AgCl) in an aqueous solution containing 0.1 M pyrrole and 0.2 M sodium nitrate. The overoxidation of PPy film was carried out in 0.1 M NaOH solution by cycling the potential between +0.80 and +1.20V at 50mV s(-1). The PPy film exhibited good sensitivity toward, especially, fluoride and chloride ions. The lowest detection limit (3 sigma) observed was 10(-8) M for fluoride with PPy detector. This is the first study using OPPy electrode for the potentiometric detection of both monovalent and divalent cations in literature. The correlation coefficients obtained from the calibration curves were 0.947-0.991 for anions and 0.998-0.999 for cations. The response of ions at the PPy and OPPy electrodes maintained over 90-94% of the original value for 45 and 30 days, respectively. It can be concluded from the observed data that these electrodes can be used as an alternative detector materials to analyse anions and cations in the water samples by ion chromatography. (C) 2008 Elsevier B.V. All rights reserved.