| An improved chemical method for the determination of the molar substitution degree of hydroxyethyl guar gum has been described. The hydroxyethyl groups are totally cleaved from modified galactomannans at 130℃in the presence of excess mixed p-toluenesulfonic-acetic anhydride for 14 hours, and then the products entirely hydrolyzed into ethylene glycol at pH=11 in an hour. Quantifying the mass of reaction products derived from the hydroxyethyl group, the molar substitution degree of the low-substituted hydroxyethyl guar gum can be exactly estimated.
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