Multifaceted approach for determining the absolute values for lignin subunits in lignocellulosic materials

Abstract

Quantifying the cell wall polymers in wood and plants has been a tremendous challenge because no single method can achieve absolute quantification of any cell wall polymer. Two-dimensional NMR spectroscopic techniques have advanced this area with the introduction of wood dissolution and cryogenically cooled probes, allowing for semi-quantification. However, a more robust technique had to be developed to allow for a more absolute quantification of cell wall polymers. This study explored a multifaceted approach to accurately quantify lignin methoxyls using gas chromatography and mass spectroscopy so as to normalize the methoxyl peak in the two-dimensional NMR spectra. This made it possible for any well-dispersed peak in the spectra to be accurately quantified. Several lignin model compounds were analyzed to test the accuracy of the methoxyl analysis, and several lignocellulosic materials were tested using this approach. The results showed that the methoxyl analyses of the model compounds were useful in confirming the accuracy of the method, which allows for faster and more robust methoxyl analysis of the lignocellulosic materials. The importance of this study relates to a fundamental understanding of what specific cell wall polymers are being modified during chemical, biological, or other modification of lignocellulose.

Citation

Yelle, Daniel J. 2020. Multifaceted approach for determining the absolute values for lignin subunits in lignocellulosic materials. Res. Note. FPL-RN-0384. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 7 p.