Development of a Portable NMR Device for Quantitative Detection of Norfloxacin (A Veterinary Drug) in Animal-Derived Food Products

Highlights Development of a portable NMR platform with a miniaturized bipolar plate magnet and optimized RF probe. Validation of device performance through precise measurement of T2 relaxation time. Rapid and quantitative detection of norfloxacin veterinary drug using immunomagnetic nanoparticles. High sensitivity and linearity for norfloxacin detection. Abstract. Magnetic relaxation switching (MRS) biosensors offer rapid, quantitative detection of veterinary drug residues in animal-derived food products. However, traditional nuclear magnetic resonance (NMR) instruments remain cost-prohibitive and impractical for field deployment. To address this limitation, we developed a portable NMR device centered on a miniaturized bipolar plate magnet and an optimized radio frequency (RF) probe. The developed NMR device’s performance was validated using a CuSO 4 ·5H 2 O aqueous solution (copper sulfate pentahydrate dissolved in water), achieving stability and accuracy comparable to commercial benchtop NMR systems. Further experiments with 30 nm magnetic particles demonstrated a linear correlation between nanoparticle concentration and transverse relaxation time (T 2 ). Leveraging immunomagnetic nanoparticles functionalized for norfloxacin recognition, the device detected this veterinary drug with a limit of detection (LOD) of 1.63 ng/mL and a linear detection range of 5 to 100 ng/mL with R 2 = 0.98. These results suggest the system’s potential for quantitative on-site analysis. The compact, cost-effective platform developed in this study holds significant promises for enhancing food safety monitoring in supply chains, markets, and laboratories, enabling rapid regulatory compliance tests of veterinary drug residues in animal-derived food products. Keywords: Keywords.,Magnet optimization, Portable NMR, Solenoid coil optimization, Veterinary drug residues.