In this article a sensitive differential pulse stripping voltammetry technique on Nafion-coated bismuth-film electrode (NCBFE) was studied for the simultaneous determination of zinc, cadmium, and lead ions in blood samples at ultra trace levels. The measurement results were in excellent agreement with those obtained from atomic absorption spectroscopy. Various operational parameters were investigated and discussed in terms of their effect on the measurement signals. Under optimal conditions, calibration curves for the simultaneous determination of zinc, cadmium, and lead ions were achieved, based on three times the standard deviation of the baseline, the limits of detection were 0.09 mg L À1 for Cd(II), 0.13 mg L À1 for Pb(II), and 0.97 mg L À1 for Zn(II) respectively.

A nanostructured gold modified glassy carbon electrode (Au nano /GCE) was employed for the determination of trace chromium(VI). To prepare Au nano /GCE, the GCE was immersed into KAuCl 4 solution and electrodeposition was conducted at the potential of -0⋅4 V (vs Ag/AgCl) for 600 s. Scanning electron microscopy measurements show that the electrochemically synthesized gold nanoparticles were deposited in aggregated form. Any undue effects caused by the presence of foreign ions in the solution were also analysed to ensure that common interference in the determination of chromium(VI) by square wave voltammetry, do not influence the electrochemical response of the latter element. The results show that this method allows for Cr(VI) determinations with a much lower detection limit (0⋅01 µg L -1 ) in the presence of excess of Cr(III) than the commonly used diethylenetriammine pentaacetic acid (DTPA) method. The method was applied to determine levels of chromium(VI) in tap water and sewage water.

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The interaction between captopril, an inhibitor of angiotensin converting enzyme and human serum albumin, a principal plasma protein in the liver has been investigated in vitro under a simulated physiological condition by UV-vis spectrophotometry and fluorescence spectrometry. The intrinsic fluorescence intensity of human serum albumin was strongly quenched by captopril. The binding constants and the number of binding sites can be calculated from the data obtained from fluorescence quenching experiments. The negative value of G 0 reveals that the binding process is a spontaneous process. According to the van't Hoff equation, the standard enthalpy change (H 0 ) and standard entropy change (S 0 ) for the reaction were calculated to be 35.98 KJmol -1 and 221.25 Jmol -1 K. It indicated that the hydrophobic interactions play a main role in the binding of captopril to human serum albumin. In addition, the distance between captopril (acceptor) and tryptophan residues of human serum albumin (donor) was estimated to be 1.05 nm according to the Förster's resonance energy transfer theory. The results obtained herein will be of biological significance in pharmacology and clinical medicine.

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