The electrochemical potentials for free or immobilized Cratylia mollis seed lectin (Cra). were obtained through potentiostatic techniques. A saline solution was used as support to control the charge distribution between saturated calomel electrode and platinum electrode (working electrode). The electrochemical potential to free Cra was determined at the following concentrations: 0.6, 0.9 and 1.0 mg/ml in an aerated environment under different temperatures (5, 10 and 20 degreesC). The best electrochemical potential was obtained with 1.0 mg/ml, at 5 and 10 degreesC, 87 and 102 mV, respectively. Electrochemical potential to Cra immobilized on glass beads activated with 3-aminopropyltriethoxysilane described a linear behavior in relation to the increase in glucose concentration. The development of techniques to define interface electrical parameters will be able to give information about charged groups adsorbed to electrode surface revealing interactions particularly in biological systems. (C) 2003 Elsevier Science Ltd. All rights reserved.