Table 1.
Carbon distribution (%) in different chemical shift regions (ppm) in 13C-CPMAS-NMR spectra of lignins from cardoon (CAR), eucalyptus (EUC), black poplar grown in Ripiti (RIP) and black poplar grown in Limatola (LIM).
| Lignin Extracts | Chemical Shift Regions | Indexes | ||||||
|---|---|---|---|---|---|---|---|---|
| 187–162 (COOH) | 162–112 (aromatic-C) | 112–93 (anomeric-C) | 93–46 (C-O, C-N) | 46–0 (Alkyl-C) | HB | HI | HB/HI | |
| CAR | 4 | 20 | 11 | 48 | 17 | 37 | 63 | 0.59 |
| EUC | 6 | 11 | 7 | 38 | 38 | 49 | 51 | 0.96 |
| RIP | 7 | 19 | 9 | 40 | 25 | 44 | 56 | 0.79 |
| LIM | 7 | 20 | 10 | 44 | 19 | 39 | 61 | 0.64 |
HB = (162–112) + (46–0); HI = (187–162) + (112–46); HB/HI = (162–112) + (46–0)/(187–162) + (112–46).