Objective   A rapid method for detecting residues of enrofloxacin (ENR) and ciprofloxacin (CIP) in seafood by surface-enhanced Raman spectroscopy (SERS) was developed.

  Method   On spiked seafood samples, (50±5) nm silver nanoparticles were used as the enhancement reagent and 200 g·L⁻¹ NaCl solution as the extraction solution for the SERS assay. Detection results were read within 3 min and mathematical correlation between peak measurement and drug concentration examined. Based on the linearity and limit of detection, optimal assay conditions were determined.

  Result  The assay showed several peaks on ENR and CIP standards. The C-N bending vibration caused the peak at 532 cm⁻¹, the out-of-plane bending vibration at 552 cm⁻¹, the C-N, C-C-F out-of-plane and C-C=O in-plane bending vibrations at 651 cm⁻¹, the stretching vibration of C-H on the benzene ring, C-C=O out-of-plane bending vibration, C-C-N bending vibration and C-H, C-N stretching vibration at 737 cm⁻¹, and the C-H, C-N out-of-plane bending vibration at 785 cm⁻¹. By quantifying the characteristic peak at 737 cm⁻¹, a linear relationship with an R²＞0.96 was found between the Raman intensity and drug concentration in the range of 10–200 ng·mL⁻¹. The assay had a recovery rate of 78.4%~106.7%, RSD of 2.1%~6.7%, and a detection limit of 10 μg·kg⁻¹.

  Conclusion  The newly developed rapid SERS assay for detecting ENR and CIP residues in seafood was deemed accurate, stable, and applicable for field screening and testing.