Linear ramp cyclic voltammetry and ac impedance spectroscopy have been used to investigate the electroactivity of Zeneca products and filtration solvents using platinum microelectrodes. Linear ramp cyclic voltammetry has been used to establish appropriate excitation potentials which will minimise electrochemical reactions associated with the product or the solvent during impedance process tomography measurements. Impedance spectroscopy has been used to resolve the electrochemical impedance and the geometric impedance of a small scale test rig. This technique offers a method of establishing the appropriate frequency range of the excitation potential for use in impedance tomography measurements. (C)2000 Elsevier Science S.A. All rights reserved.