Fig. 1. Raman spectrum of nitrofurantoin standard products (a) and honey SERS spectrum (b) containing nitrofurantoin

Fig. 2. Surface enhanced Raman spectra of honey containing nitrofurantoin after baseline deduction

Fig. 3. Raw spectra (a) of 20 mg·kg^-1 nitrofurantoin honey and spectra (b) calibrated with Raman characteristic peaks at 739 cm^-1

Fig. 4. Linear relationship between nitrofurantoin concentration and Raman strength at 1 353 cm^-1 (a) and 1 612 cm^-1 (b) before and after internal standard calibration

Fig. 5. Surface enhanced Raman spectra of nitrofurantoin honey
(a): Before correction; (b): After correction

Fig. 6. Comparison of validation set models before and after correction of 1 612 cm^-1
(a): Calibration set; (b): Verification set