CoFe2O4 Nanoparticles as Oxidase Mimic-Mediated Chemiluminescence of Aqueous Luminol for Sulfite in White Wines

Recently, the intrinsic enzyme-like activity of nanoparticles (NPs) has become a growing area of interest. However, the analytical applications of the NP-based enzyme mimetic are mainly concentrated on their peroxidase-like activity; no attempts have been made to investigate the analytical applications based on the oxidase mimic activities of NPs. For the first time, we report that CoFe2O4 NPs were found to possess intrinsic oxidase-like activity and could catalyze luminol oxidation by dissolved oxygen to produce intensified chemiluminescence (CL). The effect of sulfite on CoFe2O4 NP oxidase mimic-mediated CL of aqueous luminol was investigated. It is very interesting that when adding sulfite to the luminol-CoFe2O4 system, the role of sulfite in the luminol-CoFe2O4 NP-sulfite system depends on its concentration. At a relatively low concentration level, sulfite presents an inhibition effect on the luminol-CoFe2O4 NP system. However, it does have an enhancement effect at a higher concentration level. Investigations on the effect of the solution pH and luminol and CoFe2O4 NP concentrations on the kinetic characteristics of the studied CL system in the presence of trace sulfite suggested that the enhancement and inhibition of the luminol-CoFe2O4 NP-sulfite CL system also depended on the solution pH. It seems that the concentrations of luminol and CoFe2O4 NPs did not influence the CL pathway. The possible mechanism of the luminol-CoFe2O4 NP-sulfite CL system was also discussed. On this basis, a flow injection chemiluminescence method was established for the determination of trace sulfite in this study. Under the optimal conditions, the proposed system could respond down to 2.0 x 10(-8) M sulfite. The method has been applied to the determination of trace sulfite in white wine samples with satisfactory results. The results given by the proposed method are in good agreement with those given by the standard titration method.