The degree of hydrophobicity of chalcopyrite was determined by contact angle measurements on polished chalcopyrite surface in electrochemically controlled conditions. Results have shown that the increase in solution pH adversely affect hydrophobicity due to heavy surface oxidation. Maximum contact angles were measured at moderately oxidizing potentials, which proposed that slight oxidation is necessary for a hydrophobic chalcopyrite surface. Sodium diisobutyl dithiophosphinate (DTPI) displayed better results than potassium diethyl dithiophosphate (DTP): even at highly oxidizing potentials, contact angle did almost not change in the presence of DTPI as compared with the collectorless condition and in the presence of DTP. (C) 2004 Elsevier B.V. All rights reserved.