Table 1.
General band assignments of mid-IR spectrum of plants based on the literature.
| Frequency (cm−1) | Definition of the Spectral Assignments |
|---|---|
| 3500−3200 | O-H and N-H stretch: carbohydrates, proteins, alcohols and phenolic compounds |
| 2960−2950 | CH3 asymmetric stretching: mainly lipid with a little contribution from protein, carbohydrate, and nucleic acid |
| 2930−2920 | CH2 asymmetric stretch: mainly lipid with a little contribution from protein, carbohydrate, and nucleic acid |
| 2875−2870 | CH3 symmetric stretch: mainly protein with a little contribution from lipid, carbohydrate, and nucleic acid |
| 2860−2840 | CH2 symmetric stretch: mainly lipids with a little contribution from protein, carbohydrate, and nucleic acid |
| 1745−1730 | Saturated ester C=O stretch: phospholipid, cholesterol ester, hemicellulose, pectin, lignin, suberin/cutin esters |
| 1650−1630 | Amide I (C=O stretch): protein, pectin, water associated cellulose or lignin, alkaloids |
| 1630−1620 | C=C stretch: phenolic compound |
| 1610−1590 | C=O aromatic stretch: lignin, alkaloid |
| 1560−1540 | Amide II (C=N and N–H stretch): mainly protein |
| 1515−1505 | C=C aromatic stretch: lignin |
| 1460−1455 | Amide III (aromatic hydrocarbons): mainly protein |
| 1455−1440 | C–H asym bending of CH2 and CH3: cell wall polysaccharide, lipid and protein |
| 1430−1420 | O–H bend: cell wall polysaccaride, alcohol, and carboxylic acid |
| 1380−1370 | C–H sym bending of CH2 and CH3: cell wall polysaccharide, lipid and protein |
| 1375−1365 | C–H bend: cellulose and hemicellulose |
| 1250−1240 | C=O stretch: pectic substances, lignin, hemicellulose, suberin/cutin esters |
| 1235 | Amide IV (C=N and N–H stretching): mainly protein |
| 1235−1230 | C–O stretch: lignin, xylan |
| 1205−1200 | O–H in plane bend: cellulose |
| 1170−1160 | C–O–C asym stretch: cutin |
| 1160−1150 | Symmetric bonding of aliphatic CH2, OH, or C–O stretch of various groups: cell wall polysaccaride |
| 1145−1140 | C–O–C asym stretch: cellulose (β-1.4 glucan) |
| 1110−1105 | C–O–C sym stretch: cutin |
| 1105−1100 | Antisymmetric in-phase: pectic substance |
| 1085−1075 | C–O deformation: secondary alcohol, aliphatic ester |
| 1075−1070 | C–O ring stretch: rhamnogalactorunan, b-galactan |
| 1065−1060 | C–O stretch: cell wall polysaccarides (glucomannan) |
| 1045−1030 | O–H and C–OH stretch: cell wall polysaccarides (arabinan, cellulose) |
| 990−980 | C–O stretch: cutin |
| 900−890 | C–H deformation: arabinan |
| 895−890 | C–O valence vibration: galactan |
| 875−870 | C–O stretch: β–d-fructose |