MOLECULAR-WEIGHT MANIPULATION OF CHITOSAN .2. PREDICTION AND CONTROL OF EXTENT OF DEPOLYMERIZATION BY NITROUS-ACID

The molecular size of chitosan can be precisely modified by depolymeri zation with nitrous acid. The stoichiometry and specificity of the rea ction, together with the simplicity of the reaction kinetics, provide the basis for derivation of a theoretical expression that relates the number-average molecular weight (M(n)) of chitosan before and after de polymerization to the mass ratio of nitrous acid added to chitosan ori ginally present. The simplicity of the expression and the lack of limi ting assumptions in its derivation permits its use for the determinati on of the amount of nitrous acid required to degrade chitosan to a spe cified molecular weight or for the estimation of the M, of high molecu lar weight chitosan. Optimized experimental conditions are identified for quantitative application of the method.