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Table 1 Signal assignment and relative intensities in FTIR spectra of lignins

From: Differences in the adsorption of enzymes onto lignins from diverse types of lignocellulosic biomass and the underlying mechanism

Assignment Peak cm-1 KL CL AL PL ACL ASL
O-H stretching in aromatic and aliphatic hydroxyl groups 3,446 2.00 1.69 1.62 1.54 5.56 5.25
C-H vibrations in the methyl and methylene groups 2,938 0.56 0.42 0.49 0.55 0.70 0.64
  2,879 0.36 0.30 0.33 0.26 0.34 0.30
  2,845 0.31 0.22 0.29 0.30 0.40 0.36
Nonconjugated carbonyl groups (C = O stretch) 1,724 0.58 1.12 0.69 0.46 - -
Aromatic skeleton vibration 1,594 1.17 1.25 1.05 0.73 - -
  1,507 1.00 1.00 1.00 1.00 1.00 1.00
  1,422 0.79 0.66 0.73 0.40 0.55 0.43
C-H deformations and aromatic ring vibrations (methyl) 1,462 1.01 0.89 0.95 0.61 0.54 0.47
Phenolic hydroxyl groups 1,384 0.47 0.61 0.46 0.14 - -
Syringyl ring breathing, C-O stretch 1,329 0.45 0.54 0.51 0.01 0.09 0.02
Guaiacyl C-O units 1,268 0.52 - 0.82 0.64 0.74 0.89
Aromatic methyl ether bridges 1,225 0.86 1.13 0.83 0.38 1.00 0.90
  1,083 - 1.08 - 0.25 1.08 1.05
C-O stretch in ester group 1,168 - 1.01 - - 0.80 -
Aromatic C-H deformation in syringyl ring 1,123 1.85 1.38 1.37 0.47 1.54 1.26
Aromatic C-H in plane deformation G + S 1,032 1.10 1.46 0.98 0.64 1.21 1.33
Aromatic C-H out of plane C-H out of plane in position 2 and 6 of S, and in all positions of H 830 0.20 0.37 0.15 0.07 0.21 0.15
  1. The relative intensity was calculated as the ratio of the intensity of the band to the intensity of band at 1,507 cm-1. ACL, Arabidopsis Col-0 lignin; AL, aspen lignin; ASL, Arabidopsis SALK mutant 063792 lignin; CL, corn stover lignin; FTIR, Fourier transform infrared spectroscopy; G, guaiacyl; H, hydroxyphenyl; KL, kenaf lignin; PL, pine lignin; S, syringyl.