4. Conclusion
13C CP/MAS ssNMR spectroscopy provides a rapid and reliable
method to assess the lignin content of biomass. There are several
identified concerns that need to be monitored in carrying out this
analysis with high accuracy. First, due to lignin structural variation
among species of biomass [26], a standard lignin for quantification
curve calibration should be prepared using the same biomass
material to obtain a uniform standard. Second, changes in the
water content of samples can result in changes in the integrals
because of the 1H-13C cross polarization step employed. All samples
should be dried or lyophilized and stored under the identical
conditions for all measurements. Third, the standard curve should
be constructed or at least a point from a past calibration repeated
and subsequently used to normalize integrals from the new set of
experiments to match past values every time the assay is
performed. This evaluation is required in order to confirm