Modification of glassy carbon (GC) surfaces with phenanthroline derivatives (PDs) such as 5-amino-1,10-phenanthroline (5AP) and 5,6-diamino-1,10-phenanthroline (56DAP) is described in this study. Surface modification experiments were performed by cyclic voltammetry (CV) scanning from + 1.2 to + 2.7 V at scan rate of 100 mV/s applying 30 potential scans in acetonitrile (CH3CN) containing 1 mM PDs and 100 mM tetrabutylammoniumtetrafluoroborate (TBATFB). The presence of PDs on GC electrode was confirmed using CV, electrochemical impedance spectroscopy (EIS), contact angle measurements and ellipsometry and comparing with the results of bare GC electrode. A mechanism was proposed for the electrochemical modification of the GC electrode surface with PDs. The structure of the 5AP and 56DAP films was also discussed in the light of electrochemical and spectroscopic data. The complex-forming ability of the modified surfaces against metal cations was investigated by square-wave voltammetry (SWV). It was shown that surfaces having 1,10-phenanthroline ligands with different functional groups were quite useful for the determination of transition metal ions. Copyright © 2010 John Wiley & Sons, Ltd.