Hydrogel-based electrochemical cells for carbendazim analysis using a miniaturized sensor

Hydrogels (HG) have emerged as promising materials in electrochemistry due to properties like high water retention, tunable porosity, and excellent ionic conductivity. Their ability to function as solid-state electrolytes and support redox reactions makes them ideal for electroanalytical applications such as biosensors and environmental monitoring. This study focused on synthesizing, characterizing, and applying HG as electrochemical cells for detecting Carbendazim (CBZ) in various matrices. To achieve this, mini-sensors were fabricated using 3D pens and conductive filaments composed of PLA and graphite (3D/PLA-Gr/ME), providing a cost-effective and reproducible platform for electroanalytical applications. The HG structure consisted of polyacrylamide, synthesized in a single step under mild conditions using acrylamide as the monomer, bis-acrylamide as the cross-linking agent, and ammonium persulfate as the polymerization initiator. It was characterized using Fourier Transform Infrared Absorption Spectroscopy (FTIR), Raman Spectroscopy, Cyclic Voltammetry (CV), Scanning Electron Microscopy (SEM), and Energy-Dispersive X-ray Spectroscopy (EDS). The 3D/PLA-Gr/ME mini-sensor was characterized using SEM, CV, and Electrochemical Impedance Spectroscopy (EIS) to assess its structural and electrochemical properties. The HG was immersed in the target solution for a minimum of 8 h before electrode insertion, enabling the initiation of analysis. The electrochemical behavior of CBZ within the HG was examined using EIS and CV. The optimized Square Wave Voltammetry (SWV) method exhibited a linear working range of 2 to 15 µmol L⁻¹, delivering excellent analytical performance (L_D = 0.46 µmol L⁻¹) and high accuracy, with recovery rates between 95 % to 105 % in food and beverage samples.