Quantitative 13C NMR is one of the most powerful techniques in comprehensive lignin analysis. However, its high potential is often underutilized. In this paper we present different ways for quantification of a variety of lignin structural units and discuss different aspects of the method, such as productivity, reproducibility and the accuracy of the quantification of specific lignin units. Milled wood lignins (MWL) with very low sugar content isolated from 14 soft- and hardwood species were used as a baseline for method validation. Good correlations were found for different independent methods of the quantification of major lignin moieties. This indicates good reliability of the method not only for relative comparison of various lignin structures, but also in the absolute terms (per monomeric lignin unit). Furthermore, the quantitative 13C NMR approach was modified for the analysis of different types of technical lignins, which was more complex than the analysis of the native lignins. Various technical lignins originated from different pulping and biorefinery processes were characterized. The statistical data allowed for evaluating the accuracy in the quantification of different lignin units, which was different from that obtained for native lignins. More than 40 structural characteristics of native lignins and about 30 values for technical lignins were obtained on routine base. In addition, lignin moieties specific for certain lignin types could be also quantified. At the same time, limitations of the 13C NMR method will be discussed.

Expanding capability of 13C NMR spectroscopy in comprehensive lignin analysis

255th National Meeting (2018)

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