Electroless deposition of vanadium–Schiff base complex onto carbon nanotubes modified glassy carbon electrode: Application to the low potential detection of iodate, periodate, bromate and nitrite

The multiwall carbon nanotubes (MWCNTs) were used as an immobilization matrix to incorporate vanadium-Schiff base complex as electron transfer mediator onto a glassy carbon electrode surface. First, the preheated glassy carbon was subjected to abrasive immobilization of MWCNTs by gently rubbing the electrode surface on a filter paper supporting the carbon nanotubes. Second, the electrode surface was modified with casting 100 μL of V-complex solution (0.01 M in ACN). The cyclic voltammograms of the modified electrode in aqueous solution is shown a pair of well defined, stable and nearly reversible redox system of (V(IV)/V(V)) couple with surface confined characteristics. Combination of unique electronic and electrocatalytic properties of MWCNTs and vanadium–Schiff base complex, results in a remarkable synergistic augmentation on the response. The electrochemical behavior and stability of the modified electrode in aqueous solution at pH range 1–7 was characterized by cyclic voltammetry. The apparent electron transfer rate constant (Ks) and transfer coefficient (α) were determined by cyclic voltammetry and they were about 7 s−1 and 0.55, respectively. The modified electrodes showed excellent catalytic activity toward reduction of BrO3-,IO4-,IO3-andNO2- at unusually positive potential in acidic solution. The electrochemical reversibility, stability and catalytic activity of modified electrode prepared with incorporation of V-complex into CNTs film was compared with the film of adsorbed complex on the surface of preanodized GC electrodes. The modified electrode shows inherent stability at wide pH range, fast response time, high sensitivity, low detection limit and especially remarkable positive potential reduction of oxoanions that decreasing the effect of interferences in analysis. This modified electrode can be used as an amperometric detector for monitoring oxoanions in chromatography or flow injection systems.