Table 3.

List of chemical bands and the relative absorbance of lignocellulose in ATR-FTIR after acid EOS pretreatment with and without additives (EOS-20 mM ethanol organosolv pretreatment with 20 mM sulfuric acid, 2N 2-naphthol, NS 2-naphthol-7-sulfonate, MT mannitol, SA syringic acid)

Wavenumber	Band assignment	EOS-20 mM	20 mM + 2 N	20 mM + NS	20 mM + MT	20 mM + SA
750 cm−1	Naphthalenes	0.07 ± 0.00	0.58 ± 0.04	0.11 ± 0.01	0.10 ± 0.02	0.08 ± 0.01
815 cm−1	Naphthalenes	0.20 ± 0.00	0.66 ± 0.03	0.21 ± 0.00	0.23 ± 0.02	0.22 ± 0.00
1329 cm−1	S ring plus G ring condensed (i.e., G ring substituted in C5)	0.89 ± 0.04	0.73 ± 0.01	0.82 ± 0.00	0.82 ± 0.01	0.83 ± 0.02
1665 cm−1	Conjugated carbonyl	0.31 ± 0.00	0.29 ± 0.01	0.41 ± 0.00	0.29 ± 0.02	0.38 ± 0.00
1710 cm−1	C=O stretching in unconjugated ketones and carboxyl groups	0.41 ± 0.01	0.34 ± 0.01	0.45 ± 0.03	0.42 ± 0.01	0.43 ± 0.01
2840 cm−1	C–H stretching (CH3 and CH2)	0.37 ± 0.01	0.35 ± 0.01	0.40 ± 0.00	0.44 ± 0.02	0.36 ± 0.01
2940 cm−1	C–H stretching (CH3 and CH2)	0.48 ± 0.01	0.41 ± 0.00	0.51 ± 0.01	0.54 ± 0.01	0.48 ± 0.00
3460 cm−1	O–H stretching in aliphatic and phenolic –OH	0.45 ± 0.01	0.41 ± 0.01	0.52 ± 0.00	0.52 ± 0.01	0.46 ± 0.01