116 Introduction to Renewable Biomaterials
Cellobiose
789
Retention time (min)
10 11
Glucose
Xylose Arabinose
Figure 4.2HPLC chromatogram of four monosaccharide standards separated by Bio-Rad©RAminex
87P column at 60∘C, flow rate of 06 ml min−^1 of 4 mM H 2 SO 4.
uronic acid side groups such glucuronic acid or galacturonic acid can be detected with
HPLC but typically specific protocols, different from the main chain polysaccharides,
must be established as their interactions with the column change their retention time
significantly. While HPLC methods are common to quantify sugar components, gas
chromatography (GC) methods were also developed for sugar determination. GC
methods require the reduction of the monosaccharides into their nonreducing alditol
form and derivatizing into acetates with acetic anhydride. The samples need to be
isolated from the derivatizing solution because unreacted compounds impact peak
resolution. While the method involves additional steps that would make screening
100s of samples more difficult relative to direct injection with HPLC, it is an accurate
alternative for carbohydrate analysis (Table 4.2).
4.9 Determining Cell Wall Structures Through Spectroscopy and Scattering
4.9.1 Probing the Chemical Structure of Biomass
The structure of carbohydrate contributes to the fiber properties and ultimately
affects the product quality. Many techniques, such as X-ray diffraction (XRD),
cross-polarization/magic angle spinning (CP/MAS)^13 C NMR [15–17, 66, 67], Fourier-
transform infrared spectroscopy (FTIR), and Raman spectroscopy [68–70] have been
employed to determine chemical structure and local environment of the polysac-
charides. These techniques are nondestructive and can be used with biomass in the
as-received state. The degree of crystallinity is one of the commonly used parameters to
probe cellulose characteristics of biomass. Herein, we discuss the resulting information
from these techniques and how to correlate the obtained information with the chemical
structure of biomass.
