Table 3.

Characteristic peaks of EHL and their assignments.

Wave number/cm−1	Characteristic peaks of functional groups and their assignments
1700	Non-conjugated carbonyl
1650–1655	Conjugated carbonyl
1600–1605, 1505–1515	Vibration of aromatic skeleton
1460–1470	C-H deformation vibration of methyl or methylene
1424	C-H plane deformation vibration on aromatic nucleus
1328	Syringyl
1266–1270	Guaiaretic nuclear methoxy C-O vibration
1220–1230	C-O vibration of the aromatic nucleus related to syringyl
1167	C-O-C stretching vibration in ester bond
1125–1130	Aromatic nucleus C-H vibration
1120	In-plane bending vibration of syringyl ring C-H
1030–1036	In-plane deformation vibration of aromatic C-H
833–835	Out-of-plane bending vibration of aromatic nucleus C-H