Fabrication of bulk-modified carbon paste electrode containing α-PW₁₂O₄₀ ^3- polyanion supported on modified silica gel: Preparation, electrochemistry and electrocatalysis

α-PW₁₂O₄₀ ^3- (PW₁₂) supported on the surface of silica gel derivatized by 3-aminopropyl(triethoxy)silane (devoted briefly as SiNH₃PW₁₂) was synthesized and used as bulk modifier to fabricate a renewable three-dimensional chemically modified electrode. The electrochemical behavior of the modified electrode was characterized by cyclic voltammetry. There is an ionic bonding character between PW₁₂ and the surface amino groups of modified silica, which greatly improves the stability of SiNH₃PW₁₂-modified carbon paste electrode due to insolubility of silica gel in water. The SiNH₃PW₁₂ bulk-modified carbon paste electrode not only maintains the electrochemical activity of PW₁₂, but also exhibits remarkable advantages of renewability, as well as simple preparation and inexpensive material. The modified electrode offers an excellent and stable electrocatalytic response for the reduction of IO₃ ^- and hydrogen peroxide. The SiNH₃PW₁₂-CPE is successfully applied as an electrochemical detector to monitor IO₃ ^- in flow injection analysis (FIA). The catalytic peak current was found to be linear with the IO₃ ^- concentration in the range 5 × 10^-6 to 1 × 10^-3 mol L^-1. The detection limit of the proposed method was found to be 3.1 × 10^-6 mol L^-1 for IO₃ ^- determination.