How is the degree of substitution defined and determined for starch modified with Quat 188?
The degree of chemical modification may be expressed in several ways. Because the reaction with Quat 188 involves substitution at the hydroxyl groups, the average number of substituents per anhydroglocose unit is the degree of substitution (D.S.). A D.S. of 1.0 indicates an average of one cationic substituent for each anhydroglucose unit; maximum possible D.S. is 3.0. Degree of substitution is calculated using the following equation: DS= (162xW) ÷ [100x M – (Wx 151)] Where: 162=Molecular weight of Anhydroglucose. W=% Nitrogen on a dry basis. M=14= Molecular weight of Nitrogen. 151 = Molecular weight of the cationic substituent group.
