Thermally assisted hydrolysis and methylation of milled beech leaf litter

Thermally assisted hydrolysis and methylation (THM) with tetramethylammoniu m hydroxide (TMAH) of milled beech leaf litter was used to investigate the behaviour of polysaccharides, lipids and lignin components in complex organ ic matrices. THM at 300 degrees C produced a limited fragmentation of ligni n derivatives and the relative proportion of fatty acid methyl esters incre ased with respect to aromatic compounds when compared with THM at 500 degre es C. Polysaccharide pyrolysis products were minor compounds at both temper atures. In addition, three different procedures for TMAH reaction at 300 de grees C were tested. Method A consisted in the application of TMAH solution to the sample, drying with a N-2 flow and immediate insertion in the pyrol yser. In method B the sample plus TMAH was sonicated for 30 min. In method C the sample was maintained with TMAH for 48 h at room temperature. It was shown that a prolonged time of reaction and/or disruption of structures by sonication and more intensive mixing with TMAH increases the yield of evolv ed products. Therefore, it is proposed that a standardization of the pretre atment procedure with TMAH is needed in order to compare results obtained b y different authors. (C) 1999 Elsevier Science B.V. All rights reserved.