Dual-functional AgPW/graphene composite for self-referenced ratiometric electrochemical determination of Sudan I

Sudan I is a lipophilic azo dye that is illegally used as a food colorant and poses potential risks to human health. Developing a rapid and sensitive determination method for Sudan I is of significance. Here, a novel ratiometric electrochemical sensing platform is developed by integrating Ag₃PW₁₂O₄₀ (AgPW) with the cetyltrimethylammonium bromide-modified graphene composite (AgPW/CTAB-Gr). AgPW enhances the electrochemical oxidation response of Sudan I while simultaneously providing a stable intrinsic redox signal for internal calibration. Meanwhile, the large specific surface area and excellent electrical conductivity of graphene provide binding sites for Sudan I and facilitate charge transfer. Benefiting from the distinctive performance displayed by AgPW/CTAB-Gr composites, the proposed sensor exhibits a wide linear range of 0.1-1000 µM for Sudan I. The sensor is successfully applied to the determination of Sudan I in real samples, achieving recoveries of 97.20-105.38%. By integrating electrocatalytic enhancement and internal calibration within the same POM component, the proposed AgPW/CTAB-Gr platform provides a simple ratiometric sensing strategy without the need for an additional electroactive reference probe.