The present study introduced a novel ion-pair complex of [Co(5,5´-dmbpy)3][Ce(NO3)6] (a1) fabricated by the reaction of Co(NO3)26H2O, Ce(NO3)36H2O, NaNO3 and 5,5´-dimethyl-2,2´-bipyridine ligand. A sonochemical method was used to synthesize the nano-scale [Co(5,5´-dmbpy)3][Ce(NO3)6] (a2). The sulfite was then detected and quantified on a carbon paste electrode (CPE) modified with ferrocene derivative and cobalt nanoparticles (Co-NPs). Scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) were employed to characterize the Co-NPs. The results showed a significant improvement in the electrocatalytic activity and electro-active surface area following the CPE surface modification with the ferrocene derivative and Co-NPs. The voltammetric detection of sulfite was performed successfully by the as-fabricated sensor in real samples, with the linear dynamic range and the limit of detection of 0.07–440.0 and 0.03 lM, under optimal conditions, respectively.
