A volcanic ash-based geopolymer (GPVA) was used to design an electrochemical sensor for the determination of sunset yellow (SY) in nonalcoholic juices. After the preparation and characterization of the geopolymer material, it was used to modify a carbon paste electrode (GPVA-CPE). The electrochemical impedance spectroscopy (EIS) characterization results of the GPVA-CPE showed faster electron transfer than those of the carbon paste electrode (CPE). Cyclic voltammetry (CV) using [Fe(CN)6]3- ions as redox probes showed an accumulation of [Fe(CN)6]3- ions on the surface of the GPVA-CPE. The electrochemical response of the modified electrode, GPVA-CPE, for the electroanalysis of sunset yellow was significantly improved compared to that of the carbon-paste electrode, CPE. Several parameters affecting the accumulation and detection steps were optimized using square wave voltammetry (SWV). Optimal voltammetric detection of SY was obtained with 3 mg of geopolymer as the CPE modifier and 240 s of accumulation time in Britton–Robinson buffer (0.1 M, pH 7). Under optimal conditions, the sensor exhibited a linear response in the concentration range of 0.02–0.1 µM, and the detection limit of sunset yellow was found to be 6.37 nM (S/N = 3). The interference of some ions on the oxidation peak of sunset yellow on the GPVA-CPE was also evaluated, and no significant interference was observed, demonstrating the selectivity of the sensor. The sensor was applied to the analysis of three commercial juices, and the results were consistent with those obtained using UV–vis spectroscopy. The developed method has the potential for routine quality control of commercial juices.

Geopolymer, volcanic, ash, food colorant, voltammetry, soft drink