Eco-friendly nickel-ferrite/chitosan composite for electrochemical sensing of Erythrosine B

• A novel NiFe 2 O 4 -CS based sensor was fabricated for sensitive ERT-B detection. • The sensor achieved excellent repeatability and selectivity towards ERT-B. • DFT calculations show that the xanthene benzoate and benzoic acid parts of ERT-B are key electron transfer sites. • Voltammetric and MC simulations showed optimal interaction and stability between ERT-B and NiFe 2 O 4 -CS. Erythrosine B (ERT-B), a poly-iodinated xanthene dye is approved by the World Health Organization (WHO) and the US Food and Drug Administration (FDA) as an additive in food, pharmaceuticals and cosmetics. However, excessive consumption of ERT B has been linked to endocrine disruption, mutagenicity and carcinogenicity, making its real-time detection is highly imperative. This study presents the rapid synthesis of nickel ferrite nanoparticles (NiFe 2 O 4 ) from grapefruit peel extract and the development of an innovative, cost-effective electrochemical sensor for ERT-B detection. The electrochemical behaviour of ERT-B was examined using cyclic voltammetry (CV), square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS). The sensor, fabricated by modifying a glassy carbon electrode (GCE) with NiFe 2 O 4 and chitosan (CS), exhibited excellent catalytic activity for the detection of ERT-B in food samples. Density functional theory (DFT) calculations supported the electrochemical oxidation of ERT-B, confirming its chemical reactivity with an energy band gap of −1.281 eV. The CV and SWV results showed that the GCE-NiFe 2 O 4 -CS sensor displayed good sensitivity and antifouling properties. Under the optimized parameters, the limit of detection over the 2.91–39.93 µM concentration range was found to be 1.04 µM using SWV. The practical applicability of the sensor in selected food samples yielded satisfactory recovery rates ranging from 92.5–108.5 % and good precision (relative standard deviation <4 %), demonstrating the high reliability of the sensor for real-time analysis of ERT-B in food samples. Additionally, the adsorption energy values from Monte Carlo (MC) simulations indicate strong stability and interactions between ERT-B and the sensing catalyst (NiFe 2 O 4 -CS).