Smartphone electrochemical sensor based on laser-induced graphene integrated electrode for on-site sulfadimidine detection in beef and milk.

Sulfadimidine (SM2), a potentially carcinogenic sulfonamides, poses a threat to food safety. In this study, a portable electrochemical sensing platform integrated with a smartphone is developed for on-site sulfadimidine (SM2) detection. The electrode utilizes a flexible three-electrode system based on laser-induced porous graphene (LIPG), fabricated via CO₂ laser etching of polyimide (PI) film. The platform is wirelessly connected to a portable electrochemical workstation and smartphone via Bluetooth. Laser parameters, including power and etching depth, are optimized to improve electrochemical performance. The optimized LIPG electrode exhibits significantly improved sensitivity-2.87 and 10.87-fold higher than screen-printed carbon electrode (SPCE) and glassy carbon electrode (GCE), respectively-along with excellent stability (RSD < 0.46% over 99 cycles) and a rapid 10 s response time. Quantitative detection of SM2 demonstrates good linearity (3 - 110 μM, R2 = 0.999), with low limits of detection (LOD) of 0.03 μM and quantification (LOQ) of 0.1 μM. The method is validated in spiked beef (recovery 93.34% - 103.70%) and milk (recovery 98.50% - 100.80%), confirming its practical applicability. This work is novel in systematically linking laser processing parameters to LIPG electrochemical performance and significant in demonstrating a field-deployable, cost-effective, and smartphone-enabled strategy for monitoring SM2 residues.