We describe here a voltammetric method based on the ion transfer at a water/oil interface for the electrochemical study of the interaction between high molecular weight dsDNA and two molecules of biological interest: the anthracycline drug daunorubicin (DNR) and the neurotransmitter dopamine (DA). The binding constants of the complexes were determined by performing an amperometric titration, following the decrease of ion transfer currents upon addition of dsDNA, using differential pulse voltammetry (DPV) technique. Binding constants were interpreted in terms of the main interaction mode of the molecules with DNA. A binding constant of 1.7 x 10(4) M-1 was obtained for the intercalation complex of DNR into DNA base pairs (bp), while a binding constant of 1.8 x 10(3) M-1 was obtained for the electrostatic interaction between positively charged DA and negatively charged dsDNA, using a non-linear binding model. The binding site size, in terms of base pairs, for the interaction between the two molecules and DNA was also estimated using non-linear regression analysis. Two binding site models were tested and compared in this work. (C) 2015 Elsevier Ltd. All rights reserved.