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) natural cellulose fibres (cotton). The results were correlated with those obtained from the conventional methylene blue method. Both methods shoe excellent correlation. The progress of the cellulose fibre oxidation was monitored using viscosimetric determination of molecular weight. The content of carboxyl groups depends on the oxidation procedure and is, in the case of selectively oxidized fibres, twice as high as the content of carboxyls in raw fibres. The carboxyl group content for non-selectively oxidized fibres increased by approximately 180%, relative to untreated fibres. The results of our investigation demonstrate clearly that complexometric titration is an excellentn 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 fibres.