LIGNIN QUANTITATION BY FT-RAMAN SPECTROSCOPY

Because of the structural complexity of biomass, quantitation of lignin in a variety of wood and plant cell walls is difficult. Consequently, to measure lignin in different plant species, a number of different methods exist. The methods can give different values for the same material samples and such differences result from the nature of the biomass. In the past, although there have been many applications of Raman spectroscopy in the studies of lignin, so far, for most materials, quantitation of lignin has proven to be a challenge. In the present work, a novel approach that successfully quantified lignin is described. The strategy, in part, was based upon the minimization of the contributions to the lignin band intensity at 1600 cm(-1) by those structures that contribute to it excessively, namely chromophores and aromatic-ring conjugated units in lignin. Using a variety of samples with lignin composition in the range 4.9 to 48.4 % good linear correlations against Klason and total lignins were developed (coefficients of determination R-2 0.97 and 0.95, respectively).