Quantitative Determination of Carboxyl Groups in Cellulose by Complexometric Titration

Complexometric titration was used to determine the carboxyl group content of a series of oxidatively treated (selective and non-selective oxidation) nature cellulose fibers (cotton). The results were correlated with those obtained from the conventional methylene blue method; both methods show an excellent correlation. The progress of the cellulose fibers oxidation was monitored using viscosimetric determination of the molecular weight. The content of carboxyl groups depends on the oxidation procedure and it is, in the case of selectively oxidized fibers, twice as high as the content of carboxyls in raw fibers. The carboxyl group content for non-selectively oxidized fibers increased by approximately 180%, relative to untreated fibers. The results of our investigation demonstrate clearly that complexometric titration is an excellent tool for monitoring the influence of chemical modifications on the carboxyl group content. This method is sensitive enough to determine small changes in the content of functional groups for chemically modified fibers. __________________________________________________