Figure 4.

Reference versus predicted plot for validation set using mid-infrared, near-infrared, and Raman spectral data. (A) Plot of the predicted lignin S/G ratio using a model built from second derivative + MSC-transformed mid-infrared spectra and the reference pyMBMS data. The black line indicates the target line of optimal fit and the blue line represents the experimental fit of the data to the model. (B) Plot of the predicted lignin S/G ratio using a model built from second derivative + MSC-transformed near-infrared spectra and the reference pyMBMS data. The black line indicates the target line of optimal fit and the blue line represents the experimental fit of the data to the model. (C) Plot of the predicted lignin S/G ratio using a model built from first derivative + EMSC-transformed Raman spectra and the reference pyMBMS data. The black line indicates the target line of optimal fit and the blue line represents the experimental fit of the data to the model. The x-axis shows the pyMBMS measured lignin S/G ratio, and the y-axis reveals the predicted lignin S/G ratios. S/G = syringyl-to-guaiacyl ratio, MSC = multiplicative scatter correction, pyMBMS = pyrolysis molecular beam mass spectrometry, EMSC = extended multiplicative scatter correction.