Fig. 1. Absorption spectra of five acids

Fig. 2. (a) Absorption spectra of Vitamin B2 of different concentrations; (b) Absorption spectra of Vitamin B2 in different humidity

Fig. 3. Result of S-G filtering

Fig. 4. RNN classification network structure

Fig. 5. CNN classification network structure

Fig. 6. Spectral images of 12 materials

Fig. 7. The training process of RNN network

Fig. 8. The training process of CNN network

Fig. 9. (a) Comparative experiment of concentrations of samples; (b) Comparative experiment of data dimensions