In this research, new polymer of 4,4'-dicyanamidobiphenyl (bpH(2))-Cu(II) complex, [Cu(bp)(H2O)(2)](n), has been synthesized and characterized by FT-IR, UV-vis spectroscopy and elemental analysis. The spherical morphology of Cu nanoparticles was confirmed by scanning electron microscopy (SEM) image and the transmission electron microscopy (TEM) image showed that the particle size dimensions of Cu nanopartides were about 80 nm. Thermal gravimetric analysis (TGA) results indicated that this polymer was thermally stable. Hence, the prepared polymer was used as a modifier for the electrochemical determination of dopamine (DA) and ascorbic acid (AA). Compared to the bare carbon paste electrode (CPE) and multiwall carbon paste electrode (CNTPE), bpCu modified CPE (bpCu-CPE) exhibits much higher electrocatalytic activities toward the oxidation of dopamine and ascorbic acid with an increase in peak currents and a decrease in oxidation overpotentials. The effects of scan rate, concentration and pH were also studied. Differential pulse voltammetry results show that DA and AA could be detected selectively and sensitively at bpCu-CPE with peak-to-peak separation of 200 mV. Relative standard deviations for AA and DA determinations were less than 2.5%, and the linear response ranges of the electrode were 0.05-30.0 mu mol L-1 for AA and DA, respectively. The calculated detection limits were 0.02 and 0.04 mu mol L-1 (S/N = 3) for AA and DA, respectively. In addition, the presented method was successfully applied for the simultaneous determination of DA and AA in urine and blood samples with reliable recovery. (C) 2015 Elsevier B.V. All rights reserved.