Non-enzymatic label-free electrochemical sensor based on polyimidazole–SDS/Au nanoparticles interface for diphenylamine detection in fruit samples

This work reports the development and application of a non-enzymatic electrochemical sensor based on gold nanoparticles/polyimidazole modified screen-printed electrode (AuNPs/p-Im/SPE) for the determination of diphenylamine (DPAH) in fruit matrices. Physicochemical and electrochemical characterizations confirmed the successful formation of the conductive p-Im film and the effective anchoring of AuNPs on the SPE, which enhanced its electron transfer properties and reduced the charge transfer resistance. The AuNPs/p-Im/SPE sensor exhibited excellent analytical performance when applied for DPAH detection using differential pulse voltammetry, recording a linear response range of 20 to 200 μmol L −1 , a limit of detection of 0.43 μmol L −1 , and good selectivity in the presence of common interferents. Mechanistic studies demonstrated that the oxidation process involves two electrons and two protons under a mixed adsorption/diffusion-controlled regime. The applicability of the sensing platform was successfully validated in real fruit matrices − apple, pear, peach, nectarine, and plum, using the standard addition method. These findings showed that the AuNPs/p-Im/SPE sensor exhibited satisfactory results, which were in good agreement with those obtained from UV–vis spectrophotometry, confirming its reliability and great application potential for rapid, low-cost, and in situ food safety monitoring.