The formation constants of surface inclusion complexes were determined using a carbon paste electrode, CPE, and cyclic voltammetry for aqueous-based media containing Pb(II) and alpha, beta and gamma cyclodextrins. In order to promote the occupation of the molecular cavities in the cyclodextrins, the medium with the support electrolyte contained ClO4- ions, which have the capacity to modify the hydrophobic properties of such cavities. The results obtained were: Pb(II)-alpha(CD) K = 883.7 +/- 13.6 M-1, Pb(II)-beta(CD) K = 727.5 +/-20.2 M-1, Pb(II)-gamma(CD) K = 782 +/- 10.7 M-1. (C) 2004 Elsevier Ltd. All rights reserved.