Fig. 1. Chemical structural formula of levamisole

Fig. 2. Theoretical calculation results of levamisole hydrochloride
(a): Optimize molecular structural formula of levamisole hydrochloride; (b): Comparison between theoretical Raman spectra and solid Raman spectra

Fig. 3. SERS peak intensity at 469 cm^-1 under different detection conditions

Fig. 4. SERS spectra of levamisole hydrochloride in methanol solution with different concentrations
a—j, solid, methanol, 0.01, 0.1, 1, 10, 75, 100, 250, 500 mg·L^-1 solution respectively

Fig. 5. Linear relationship between peak intensity and concentration

Fig. 6. Comparison of extraction effects of different extraction methods
a: Solid; b: Once liquid-liquid extraction blank; c: Once liquid-liquid extraction standard addition; d: Twice liquid-liquid extraction blank; e: Twice liquid-liquid extraction standard addition

Fig. 7. Comparison of extraction effects of different extraction solvents
a: Solid; b: Ethyl acetate blank; c: n-hexane blank; d: Chloroform blank; e: Ethyl acetate extraction; f: n-hexane extraction; g: Chloroform extraction