Front Matter

 

Characterization Methods and Techniques 113

Table 4.1Selected characterization methods of structural carbohydrates and lignin.

Biomass characteristics Techniques

Composition of lignocellulose

Monosaccharide and lignin contents

• Two-step acid hydrolysis [11, 13, 14]


• High-pressure liquid chromatography (HPLC)
  Degree of crystallinity
  Changes of inter-/intramolecular hydrogen
  bonding of polysaccharides


• Cross-polarization/magic angle spinning
  (CP/MAS)^13 C nuclear magnetic resonance
  (NMR) [15–17]


• X-ray diffraction (XRD) [15–17]


• Fourier-transform infrared (FTIR) (lateral order
  index (LOI)) [15–19]
  p-Hydroxyphenyl (H): guaiacyl (G): syringyl
  (S) ratio


• FT-Raman [20–22]


• Pyrolysis-gas chromatography/mass
  spectrometry (Pyro-GC/MS) [23–26]


• 2D heteronuclear single-quantum correlation
  (HSQC) [27–31]
  -^13 C NMR [32, 33]
  Hydroxyl functional groups of lignin •Wet chemistries [34, 35]
  -^1 H NMR [34–38]
  -^13 C NMR [34, 36, 39]
  -^31 P NMR [34, 40–43]


• FTIR [34, 35]


• Ultraviolet (UV) spectroscopy [35–37]
  Lignin structural information
  Structural types and distribution of interunit
  bonding patterns of lignin
  -^13 C NMR [32, 44]


• 2D HSQC [4, 45–48]

Molecular weight distribution •Gel permeation chromatography (GPC) [49–52]

Degree of condensation of lignin •Cross-polarization-polarization-inversion

(CPPI) [53–55]

-^13 C NMR [44, 56]
-^31 P NMR [57]

there are heteropolysaccharides present that assemble onto the cellulose microfibril

surfaces. There is a lack of any evidence for any covalent bonding between the

cellulose and heteropolysaccharides, suggesting a physical association among the

components. The heteropolysaccharides are thought to help space the microfibrils

in the hydrogel-like network as the charged substituents like glucuronic acid give

rise to longer distant repulsive forces [59]. At the end of the life of the vascular cell,

monolignols are transported from the cytosol of the cell into the polysaccharide cell

wall where they undergo dehydrogenative polymerization induced by a variety of

protein-based enzymes. Side reactions occur during these processes linking lignin to

the heteropolysaccharides, usually through benzyl ether linkages or gamma carbon

esters of the propanol side chain [60].

By now it should be clear that the complex structure of the cell wall mandates careful

analytical procedures to quantify the composition of the components that go into the

cell wall. With an emphasis on the conversion and utilization of the polysaccharides,

especially glucose, for liquid fuel production, it is important to know the amount of