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Quantitative Determination of Phenolic and Total Hydroxyl Groups in Lignins

A rapid method has been developed for the determination of phenolic hydroxyl groups in lignins. The method comprises acetylation, selective aminolysis of the phenolic acetyl groups by pyrrolidine (aminolysis) and determination of the resulting 1-acetylpyrrolidine (1) by gas chromatography. A number of lignin model compounds and lignins have been studied by the method. The total amount of hydroxyl groups in lignin was estimated by complete saponification (NaOH) of the acetylated sample followed by GC-determination of the liberated acetic acid äs its benzyl ester.