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Table 2 Relative changes in poplar samples after dilute acid pretreatment by Fourier transform infrared spectroscopy

From: Effect of lignin content on changes occurring in poplar cellulose ultrastructure during dilute acid pretreatment

Band position Assignment[[32]-[38]] Pretreatment conditions
PL23-t0 PL23-t15 PL23-t35 PL19-t0 PL19-t15 PL19-t35 PL14-t0 PL14-t15 PL14-t35
3340 O-H stretching, related to cellulose-hydrogen bonds 1.7 1.6 1.5 2.1 1.9 2.2 2.1 1.8 2.3
2900 C-H stretching, related to biomass methyl/methylene group 0.8 0.8 0.9 0.9 0.8 1.0 0.9 0.8 1.1
1740 Carbonyl bonds ascribed to hemicelluloses 1.3 -- -- 1.6 -- -- 1.5 -- --
1595 Lignin aromatic ring stretch 0.7 0.8 0.8 0.6 0.7 0.7 0.5 0.5 0.7
1510 Lignin aromatic ring stretch 0.6 0.9 1.0 0.5 0.8 0.8 0.4 0.7 0.7
1424 CH2 scissor motion in cellulose 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1367 Aliphatic C-H stretch in CH3 1.1 0.9 0.8 1.3 1.1 1.1 1.4 1.2 1.1
1265 Ester absorption associated with uronic acid -- 1.1 1.2 -- 1.2 1.1 -- 1.3 1.2
1240 C-O absorption from acetyl group cleavage 1.6 1.3 1.2 2.2 1.1 1.0 2.0 1.2 1.1
1059 C-O stretch in secondary alcohol 5.0 3.6 3.4 -- 4.0 4.3 -- 5.3 4.9
1100/900 Crystalline to amorphous cellulose ration 3.0 4.4 4.5 2.9 3.7 4.5 2.7 4.1 4.4
750/710 Iα/Iβ 0.9 0.6 0.4 0.3 0.3 0.2 0.3 0.3 0.2
900 Amorphous cellulose 1.1 0.6 0.6 1.2 0.8 0.8 1.2 0.9 0.7
  1. Sample code with definition is in Table 1.