Pyrolysis gas chromatography mass spectrometry analysis of phenolic and etherified units in natural and industrial lignins

Milled-wood lignin (MWL) from Carpinus betulus, Eucryphia cordifolia, Picea . abies, Pinus sp, and Bambusa sp., Kraft lignin from Fagus sylvatica and E ucalyptus globulus, and alkali lignin and hemicellulose-linked lignin from Triticum aestivum, were investigated with respect to their composition fn p henolic and etherified phenylpropanoid H (p-hydroxyphenyl), G (guaiacyl) an d S (syringyl) units. For this purpose, a methodology based on lignin perme thylation, followed by pyrolysis-gas chromatography/mass spectrometry, and quantitation of marker compounds (H-, G- and S-type vinylphenols and their methylated derivatives) in single-ion chromatograms, was developed. The phe nolic content in the samples analyzed ranged from 2% of total units in hemi cellulose-linked lignin to near 70% ire Kraft lignins. Softwood MWL showed higher amounts of phenolic units than MWL from annual plants and hardwoods. It was found that the phenolic content of MWL from the Austral tree specie s E. cordifolia was unexpectedly high for a hardwood lignin, The significan ce of this finding in terms of lignin degradability; by-white-rot fungi, of biotechnological interest, is discussed. Copyright (C) 1999 John Wiley & S ons, Ltd.