Selective Electrochemical Sensing of Sunset Yellow in Beverages Based on Synergistic Signal Amplification of HKUST1 and MWCNTs

In this study, a highly selective electrooxidation method for sunset yellow (SY) detection in real food samples is presented on the basis of the integration of HKUST1 with multiwalled carbon nanotubes (MWCNTs) doped on a glassy carbon electrode (GCE). Cyclic voltammetry measurements of the HKUST-1-MWCNT-composite electrode revealed enhanced sensitivity for SY with a distinct redox peak potential of approximately 0.6 V, which was attributed to the highly active surface of the electrode. This response was notably more pronounced than those of tartrazine, allura red and amaranth. Electrochemical impedance spectroscopy analysis revealed a low charge transfer resistance (R_ct) for the GCE-HKUST-1-MWCNT electrode, indicating that the integration of HKUST−1 and MWCNTs significantly enhanced the electrical conductivity. In addition, Monte Carlo simulations revealed that a single copper paddle wheel (the secondary building unit of HKUST−1) greatly enhanced the dispersion of the MWCNTs within the matrix. Notably, revealing that the preferred adsorption site of SY was within the inner surface of the MWCNTs, leading to signal amplification. Overall, the sensor achieved limits of detection and limits of quantification of 1.03 and 3.44 μM, respectively, within a defined linear dynamic range. Furthermore, the sensor demonstrated strong practical applicability in real sample analysis, with an excellent recovery rate ranging from 83.11 to 114%. This sensing technique shows great promise for the selective monitoring and detection of synthetic colourants in the food sector.