Softwood lignin content

Steps in the calculation of softwood lignin content based on the UV absorbance of isodensity areas (Fukazawa and Imagawa 1981, Takano et al. 1983) are as follows ... 

We wish therefore to suggest that since all studies of lignin degradation have accounted for no more than about 50% and 25% of the initial lignin content of hardwoods and softwoods, respectively, that only the accessible side-chain portion of the lignin has been involved in such degradations. Indeed, little may be known about the chemical nature of the rest of the lignin substance in each case. Therefore it seems advisable to con-... 

Mooney, C. A., Mansfield, S. D.,Touhy, M. G., and Saddler, J. N. 1998.The effect of initial pore volume and lignin content on the enzymatic hydrolysis of softwoods. Bioresour. Technol., 64,113-119. 

The lignin content can be estimated from the spectrum by measuring the fractional area, A, of a band of signals between chemical shifts of 141 and 159 parts per million (ppm) relative to the total area of the spectrum. This band is assigned to C-3 and C-4 of guaiacyl units or C-3 and C-5 of syringyl units the fact that it is associated with just two carbon atoms of each structural unit means that the method can be used for both softwoods and hardwoods. 

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