A new sensitive electrochemical procedure is presented for the determination of Rutin based on the accumulation of its complex with Cu(II) onto the surface of hanging mercury drop electrode for 80 s.Then the preconcentrated Rutin-complex was analyzed by cathodic stripping square-wave voltammetry.. A sequential method is proposed for the determination of tryptophan and histidine by adsorptive cathodic stripping voltammetry using standard addition and H-point standard addition method (HPSAM). The complexes of copper(II) with the amino acids were accumulated onto the surface of a hanging mercury drop electrode for 60 s. Then the preconcentrated complexes were reduced by square wave voltammetry and the peak currents were measured. A reliable, highly selective and sensitive procedure is presented for simultaneous determination of Captopril and Thioguanine based on cathodic adsorptive stripping of Cu(I)-Captopril and Cu(I)-Thioguanine complexes on a hanging mercury drop electrode. A square wave voltammetric procedure for electroanalytical determination of Losartan and Triamterene in Britton-Robinson buffer at pH 3.0 as a supporting electrolyte containing 30 ng.ml -1 of copper ions was developed. Losartan can not be reduced at mercury electrode alone but a new peak appears at -0.25 V in the presence of copper due to the formation of complex between copper(II) and Losartan. The peak current of triamterene do not effected by the concentration of copper (II). The response of the system was found to be linear in the range of 30.0-270.0 nM for Losartan-copper(II) and two linear dynamic ranges of 0.5-200.0 nM plus 200.0-400.0 nM for Triamterene. The limits of detections were 23.7 and 0.26 nM for Losartan and Triamterene, respectively. . The direct current polarography of Triamterene indicates that the reduction of related drug is strongly dependent on the solution pH. A linear segment was found with slope value of ?63.6 mV/pH in the range of pH 2.0–6.0. The stoichiometry and complex formation constant (?) for Losartan-Cu(II), number of electrons (n) and number of proton transfers was also estimated. The interaction of morin-Bi(III) complex with calf thymus DNA was investigated with the use of Methylene Blue (MB) dye as a spectral probe by the application of UV-vis spectrophotometry, fluorescence spectroscopy and cyclic voltammetry. Increasing fluorescence is seen for Bi(III)-morin complex with DNA addition whereas decreased fluorescence is observed for Morin. Quenching fluorescence is observed for the DNA-complex by addition of MB which confirms the displacement of complex with MB. Cyclic voltammetry studies confirm the intercalation reaction. The results showed that only morin-Bi(III) complex can intercalate into the double helix of the DNA.