Evaluation of acid methanolysis for analysis of wood hemicelluloses and pectins

The efficiency of acid methanolysis toward cleavage of glucuronosyl linkages in hemicelluloses and pectins was studied. Two aldo-uronic acids (a dimer and a tetramer) were submitted to methanolysis with different acidic strength and methanolysis time. The aldo-uronic acid tetramer was only affected by the acidity of the medium, whereas the dimer was sensitive towards both reaction time and acidity. It was concluded that methanolysis of 0.5-1 mg of model compounds with 2 ml of 2 M HCl/MeOH at 100degreesC for 3-5 h was the best compromise between good cleavage of the glucuronosyl bonds ( approximate to 70%, mol/mol) and little degradation of the uronic acid released (below 20%, mol/ mol). The acid methanolysis of reference oligo- and polysaccharides verified the good accuracy of the method. The application of acid methanolysis on mechanical pulp fibres was tested on a thermomechanical pulp. (C) 2002 Elsevier Science Ltd. All rights reserved.