Fig. 1. Terahertz time-domain spectroscopy system

Fig. 2. Measurement results of penicillin sodium tablets. (a) Time domain spectra; (b) frequency spectra; (c) absorption spectra

Fig. 3. Measurement results of five penicillin sodium samples. (a) Absorption peak intensity and standard deviation; (b) relationship between absorption peak intensity and mass

Fig. 4. Measurement results of Jin Shining brand amoxicillin drugs. (a) Absorption spectra; (b) absorption peak intensity and standard deviation; (c) relationship between absorption peak intensity and mass

Fig. 5. Measurement results of Ren He brand amoxicillin drugs. (a) Absorption spectra; (b) absorption peak intensity and standard deviation; (c) relationship between absorption peak intensity and mass

Fig. 6. Measurement results of Xiu Zheng brand amoxicillin drugs. (a) Absorption spectra; (b) absorption peak intensity and standard deviation; (c) relationship between absorption peak intensity and mass

Fig. 7. Absorption spectra of three amoxicillin samples

Fig. 8. Two-dimensional structures and molecular calculation results of penicillin sodium and amoxicillin. (a) Two-dimensional chemical structure of penicillin sodium; (b) two-dimensional chemical structure of amoxicillin; (c) theoretical calculation result of penicillin sodium; (d) theoretical calculation result of amoxicillin