Analytical pyrolysis as a direct method to determine the lignin content in wood. Part 2: Evaluation of the common model and the influence of compression wood

In Part 1, a method for the quantification of the lignin content (Py-lignin) of Maritime pine and spruce wood samples directly from the pyrograms was presented (A. Alves, M. Schwanninger, H. Pereira, J. Rodrigues, J. Anal. Appl. Pyrol. 76 (2006a) 209). The good correlation found between the Py-lignin and Klason lignin content gave a common model to both species. In this work different larch species (Larix sp.) as well as varieties of European larch were used to evaluate this common model, revealing only small differences between the measured and the predicted Klason lignin contents. Compression wood was included due to the difference in lignin composition and content compared to normal wood. As the influence of compression wood was small a so-called "softwood model" including all samples was calculated (Py-lignin = 0.7325 x Klason lignin + 3.9195, R-2 = 0.94). This can be used for pine, larch, and spruce wood with the limitation of the highest and lowest values where the species-specific models lead to better results, although more than 95% of the differences between the species-specific models and the "softwood model" lie within 0.3%. It is expected that this model can predict the Mason lignin content of other softwoods. (C) 2007 Elsevier B.V. All rights reserved.