Quantitative 13C NMR Analysis of Kraft Lignins.

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Abstract
Three different kraft lignin samples and one native lignin extracted from milled wood have been analysed by 13C NMR. Both the DEPT pulse sequence for CH, CH2 and CH3 sub-spectral editing, and an inverse gated decoupling sequence for quantification of the various carbon atoms were used. By employing small correction factors for the integral intensities, the DEPT subspectra were also quantified and this made possible a comprehensive description of structural features in these lignins. The results obtained are discussed with reference to known features of the structure of lignin and the reactions taking place during kraft cooking.