New amperometric sensor for the determination of bromate, iodate and hydrogen peroxide based on titania sol-gel matrix for immobilization of cobalt substituted Keggin-type cobalttungstate anion by vapor deposition method

A new amperometric sensor was fabricated based on the immobilization of complex of Na2H6CoW11Co(H2O)O-39.14H(2)O (CoW11Co) and poly(4-vinylpyridine) (PVP) in a TiO2 sol-gel matrix by vapor deposition method. The preparation process simplified the traditional sol-gel process and prevented the cracking of conventional sol-gel derived glasses. The electrochemical behavior of the new amperometric sensor was studied in detail by cyclic voltammetry, and three reversible two-electron redox waves were observed in acidic aqueous solution in the potential range of -0.1 to -0.7 V. The sensor displays good electrocatalytic activity toward the reduction of bromate, iodate and hydrogen peroxide in acidic aqueous solution and the catalytic mechanisms were also discussed. The catalysis of the sensor towards bromate and iodate was systematically studied by amperometric method. The method gave a linear range from 2.0 x 10(-5) to 4.4 x 10(-3) M and a detection limit of 5.0 x 10(-6) M for BrO3- and 2.0 x 10(-6) to 2.8 x 10(-4) and 8.0 x 10(-7) M for IO3-, respectively. In addition, the sensor has some distinct advantages over the traditional polyoxometalate sensor. such as simple preparation process, fast response and long-term stability. (c) 2004 Elsevier B.V. All rights reserved.