TABLE 2.
PAS and DRIFT FTIR main absorption bands for fingerprint region of Chamomile (A), Cornflower (E), Birch buds (B), Hibiscus (C), Peppermint (D) and assignments.
| Sample | DRIFT, cm–1 | PAS, cm–1 | Reference, cm–1 | Bond, stretching | Functional group/compounds | References |
| Chamomile (A), Cornflower (E) | 1734 | 1735 | 1737 | C = O bond | Luteolin | Zou et al., 2005 |
| 1603 | 1605 | 1628 | C = O bond | Luteolin | Parlinska-Wojtan et al., 2016 | |
| 1374 | 1370 | 1375 | C–N stretch | Aromatic amines I, II | Dehelean et al., 2007 | |
| 1239 | 1241 | 1250 | C–H stretch and O–H deform. of carboxyl groups and bending of N–H bond | Amide III | Choong et al., 2016 | |
| 1102 | 1105 | 1109 | –C–O | Terpenoids, flavones | Lehto et al., 2018 | |
| 1050 | 1052 | 1053 | C–O–C stretch | Aromatic ethers and polysaccharides | Szymczycha-Madeja et al., 2013 | |
| Birch buds (B) | 1730 | 1731 | 1735 1726–1730 | C = O stretching C = O vibration | in unconjugated ketone, carbonyl, and aliphatic groups (xylan); esters, ketones, and aldehydes in hemicelluloses | |
| 1707 | 1711 | 1704 1655–1658 | absorbed OH and conjugated CO, HOH, OH bending | in lignin or cellulose absorbed water | ||
| 1455 | 1455 | 1453 | CH2 deformation stretching; CH deformation asymmetric in plane; HCH and OCH in plane bending vibration. | lignin and xylan, lignin and hemicelluloses, | ||
| 1375 | 1374 | 1372 1368–1369 | aliphatic CH stretching; CH deformation. | in methyl and phenol in cellulose and hemicelluloses, in plane CH bending; | ||
| 1256 | 1252 | 1254 1261–1263 | stretching of OCO; CO stretching; CO linkages. | guaiacyl ring; in lignin; in guaiacyl aromatic methoxyl groups | ||
| 892 | 894 | 895 | C-H COC, CCO, and CCH deformation stretching | out of plane glucose ring in cellulose and hemicelluloses and for guaiacyl rings in lignin | ||
| Hibiscus (C) | 1785 | 1784 | 1788 | R1R2C = CH2 | Methylene, overtone of δ‘ CH (out of plane) | |
| 1730 | 1739 | 1743 | vC = O | Ketone | ||
| 1612 | 1617 | 1629 | Ortho-CO-C6H4-OH | Influenced by I,M, and steric effects of substituent | ||
| 1095 | 1097 | 1098 | -C-H | In-plane CH pending modes | ||
| 1063 | 1061 | 1065 | -C-H | In-plane CH pending modes | ||
| 1028 | 1030 | 1033 | vs SO3 | |||
| Peppermint (D) | 1723 | 1725 | 1725 | C = O vibration | bonded conjugated ketones, aldehydes, quinines and esters | |
| 1630 | 1628 | 1628 | C = C vibration of aromatic structures, C = O stretching | amide I and carboxylic acids | ||
| 1439 | 1422 | 1441 | O-H in plane bend, C-O stretch vibration | carboxylic acids carbonates | ||
| 1261 | 1261 | 1250 | C–H stretch and O–H deform. of carboxyl groups and bending of N–H bond | Amide III | ||
| 1149 | 1150 | 1153 | C–O–C stretch | Aromatic ethers and polysaccharides |