Nanoporous hematite (alpha-Fe2O3) coated electrodes were applied for the investigation of the electrochemical effects of pH on adsorption of the phosphate ion to iron oxide in concentrations commonly found in natural waters. The hematite electrode was tested with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods in NaClO4 solution and in 10(-8) - 10(-4) M phosphate over the pH range 6.00 - 8.75. In cyclic voltammograms, the current features attributed to specific adsorption of H+ or OH-were accentuated by phosphate addition. Impedance studies indicated that hematite behaved like a blocking electrode with deviations to blocking behavior occurring at higher pH and with increased phosphate. Resultant spectra were modeled with an analog electric circuit with a resistor in series with three parallel lines consisting of resistive, capacitive, and constant phase elements (CPEs) highlighting processes over sections of the applied EIS frequency range. This analysis of the phosphate-hematite system may assist with the production of an electrochemical sensor for phosphate at environmentally relevant pH. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.043302jes] All rights reserved.