Redox-Active Chitosan–Imidazolium Ionic Liquid <i>-</i> MWCNT Nanohybrids on Biofiber <i>-</i> Reinforced Flexible Substrates for Sustainable Sulfite Sensing

A nonenzymatic, flexible electrochemical sensor is developed using an advanced nanocomposite comprising chitosan, an imidazolium-based ionic liquid, and multiwalled carbon nanotubes (MWCNTs) for the sensitive and selective detection of sulfite. The composite is integrated into both a glassy carbon electrode (GCE) and a biofiber-reinforced flexible strip, enabling dual-format sensing. Physicochemical and electrochemical analyses confirm that the ionic liquid and MWCNTs synergistically enhance the conductivity, film integrity, and charge transfer properties. The sensor exhibits a wide linear detection range from 70 to 20,200 μmol L–1, with a low detection limit of 1.83 μmol L–1 and high selectivity against common interferents. The flexible strip sensor also demonstrates excellent mechanical strength (6.05 MPa) and operational durability of over 50 cycles. Importantly, the sensor is successfully applied for real-time sulfite quantification in dried fruit samples, achieving accurate recovery values in complex food matrices. These results highlight the potential of this sustainable, cost-effective, and portable sensor system for advancing food safety monitoring and quality assurance practices.