Voltammetric determination of the iodide ion with a quinine copper(II) complex modified carbon paste electrode

A Cu(Qui)(NO3)(2) modified-carbon paste electrode (where Qui is quinine) wa s constructed by incorporating Cu(Qui)(NO3)(2) into a carbon-paste composed of graphite powder and Nujol. The modification with CU(QUi)(NO3)(2) result ed in a deposit of iodide ions on the electrode surface through a ligand ex change reaction. This exchange reaction was completed within 20 Ins in a CH Cl3 + CH3OH solution. The rate constant, k(0), of the ion exchange reaction was determined to be 27 s(-1) by the stopped flow spectroscopic method. Th e anodic peak of the pre-deposited iodide ion on the electrode surface was observed at + 0.54 V in a cyclic voltammogram. Various experimental paramet ers such as pH, deposition time, temperature, and electrode composition wer e optimized to analyze the iodide ion employing linear sweep and differenti al pulse voltammetry. With the exception of thiosulfate ions, inorganic ani ons did not interfere with the determination of the iodide ion. Using linea r sweep voltammetry, a calibration curve was attained over the concentratio n ranges of the iodide ion from 1.0 x 10(-4)-2.5 x 10(-6) M at the depositi on time of 10 min, with the detection limit determined as 1.0 x 10(-6) M. U sing differential pulse voltammetry, the logarithmic linear response range for the iodide ion was between 10(-6) and 10(-8) M, and the detection limit was 1.0 x 10(-8) M. This method was evaluated by analyzing the iodide ion content in a commercial disinfectant. (C) 1999 Elsevier Science S.A. All ri ghts reserved.