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 (CuFe 2 O 4 ) as building blocks. The CMCS and SA as monomers provided good film-forming and anti-fouling properties for MHG. The PDA-coated CuFe 2 O 4 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 2 − ) 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 2 − . 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.