Design of an injectable magnetic hydrogel with porous structure and electrocatalytic activity for the sensitive electrochemical detection of nitrite in foods.

Herein, we synthesized a novel injectable porous magnetic hydrogel (MHG) at room temperature using carboxymethyl chitosan (CMCS), polydopamine (PDA), sodium alginate (SA), polyethyleneimine (PEI) and copper ferrite (CuFeO) as building blocks. The CMCS and SA as monomers provided good film-forming and anti-fouling properties for MHG. The PDA-coated CuFeO as a cross-linking agent improved the homogeneity, adsorption and electrocatalytic performance of MHG, but also generated a macroporous hydrogel structure which was beneficial for sensing applications. The positive PEI enhanced the adsorption of nitrite (NO) via electrostatic attraction. The MHG modified glassy carbon electrode (MHG/GCE) sensor offered a wide linear range (0.02-2250.00 μM) and a low limit of detection (3.60 nM) for NO. Recovery tests in crispy fried pork and roast chicken yielded excellent recoveries (91.01 %-107.68 %). Analyses of commercial chicken sausage and canned luncheon meat were conducted using the MHG/GCE sensor and an ultraviolet spectrophotometry method, with the results being near identical.