Fig. 1. Determination of parameter search space

Fig. 2. Overall flow of the experiment

Fig. 3. Main measurement technology schematic diagram of spectrometric method

Fig. 4. Absorption spectrum of 94 samples with different concentrations

Fig. 5. 3D view for the first parameter optimization of Improved GS-SVR

Fig. 6. 3D view for the second parameter optimization of Improved GS-SVR

Fig. 7. 3D view for the third parameter optimization of Improved GS-SVR

Fig. 8. (a) Comparison between the predicted value of improved GS-SVR and the real value; (b) Relative error of the predicted value of improved GS-SVR

Fig. 9. (a) Comparison between predicted value and real value of different prediction models; (b) Relative error of predicted values of different prediction models